U.S. patent application number 17/275677 was filed with the patent office on 2022-02-24 for multilayer membranes, separators, batteries, and methods.
The applicant listed for this patent is Ceigard, LLC. Invention is credited to Brian R. Stepp, Geoffrey A. Tice, Eric R. White.
Application Number | 20220059904 17/275677 |
Document ID | / |
Family ID | 1000005999025 |
Filed Date | 2022-02-24 |
United States Patent
Application |
20220059904 |
Kind Code |
A1 |
White; Eric R. ; et
al. |
February 24, 2022 |
MULTILAYER MEMBRANES, SEPARATORS, BATTERIES, AND METHODS
Abstract
In accordance with at least selected embodiments, the
application, disclosure or invention relates to improved membranes,
separator membranes, separators, battery separators, secondary
lithium battery separators, multilayer membranes, multilayer
separator membranes, multilayer separators, multilayer battery
separators, multilayer secondary lithium battery separators,
multilayer battery separators, electrochemical cells, batteries,
capacitors, super capacitors, double layer super capacitors, fuel
cells, lithium batteries, lithium ion batteries, secondary lithium
batteries, and/or secondary lithium ion batteries, and/or methods
for making and/or using such membranes, separator membranes,
separators, battery separators, secondary lithium battery
separators, electrochemical cells, batteries, capacitors, fuel
cells, lithium batteries, lithium ion batteries, secondary lithium
batteries, and/or secondary lithium ion batteries, and/or devices,
vehicles or products including the same, and/or the like.
Inventors: |
White; Eric R.; (Fort Mill,
SC) ; Stepp; Brian R.; (Scottsdale, AZ) ;
Tice; Geoffrey A.; (Rock Hill, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ceigard, LLC |
Charlotte |
NC |
US |
|
|
Family ID: |
1000005999025 |
Appl. No.: |
17/275677 |
Filed: |
September 16, 2019 |
PCT Filed: |
September 16, 2019 |
PCT NO: |
PCT/US2019/051210 |
371 Date: |
March 12, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62732089 |
Sep 17, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2307/514 20130101;
H01M 50/403 20210101; B32B 2255/10 20130101; B32B 2307/581
20130101; B29B 11/14 20130101; H01M 50/417 20210101; B32B 27/18
20130101; B29K 2023/12 20130101; B32B 27/32 20130101; H01M 50/491
20210101; B32B 2307/54 20130101; H01G 11/52 20130101; B32B 2250/242
20130101; B29B 11/10 20130101; B32B 2457/10 20130101; B29K 2023/06
20130101; B32B 2307/732 20130101; H01M 50/494 20210101; B32B
2307/51 20130101; B29L 2031/3468 20130101; H01M 50/457 20210101;
B32B 2457/18 20130101; B32B 27/08 20130101; B32B 2457/16
20130101 |
International
Class: |
H01M 50/457 20060101
H01M050/457; B32B 27/08 20060101 B32B027/08; B32B 27/32 20060101
B32B027/32; B32B 27/18 20060101 B32B027/18; H01M 50/417 20060101
H01M050/417; H01M 50/403 20060101 H01M050/403; H01M 50/491 20060101
H01M050/491; H01M 50/494 20060101 H01M050/494; B29B 11/10 20060101
B29B011/10; B29B 11/14 20060101 B29B011/14; H01G 11/52 20060101
H01G011/52 |
Claims
1-59. (canceled)
60. A microporous membrane comprising: two outer layers, each outer
layer comprising a polyolefin; and a plurality of inner layers,
each inner layer comprising a polyolefin; wherein each of the outer
layers is laminated to an inner layer and each of the plurality of
inner layers is laminated to at least one other inner layer.
61. The microporous membrane of claim 60, wherein the each of the
outer layers comprises a polypropylene, a polypropylene blend, a
polypropylene copolymer, a polyethylene, a polyethylene blend, a
polyethylene copolymer, or any combination thereof.
62. The microporous membrane of claim 60, wherein each outer layer
comprises a polypropylene, a polypropylene blend, a polypropylene
copolymer, or any combination thereof.
63. The microporous membrane of claim 60, wherein the each of the
plurality of inner layers comprises a polypropylene, a
polypropylene blend, a polypropylene copolymer, a polyethylene, a
polyethylene blend, a polyethylene copolymer, or any combination
thereof.
64. The microporous membrane of claim 60, wherein there are two,
three, four, five, six or more inner layers.
65. The microporous membrane of claim 60, wherein there are three
inner layers.
66. The microporous membrane of claim 60, wherein microporous
membrane is a penta-layered membrane comprising a first outer
layer, a first inner layer, a second inner (or middle) layer, a
third inner layer, and a second outer layer.
67. The microporous membrane of claim 66, wherein the first outer
layer is laminated to the first inner layer; the first inner layer
is laminated to the first outer layer and the second inner (or
middle) layer; the second inner (or middle) layer is laminated to
the first inner layer and the third inner layer; and the third
inner is laminated to the second inner (or middle) layer and the
second outer layer.
68. The microporous membrane of claim 66, wherein the first and
second outer layers and the second inner (or middle) layer comprise
a polypropylene, a polypropylene blend, a polypropylene copolymer,
or any combination thereof.
69. The microporous membrane of claim 68, wherein the first and
third inner layers comprise a polyethylene, a polyethylene blend, a
polyethylene copolymer, or any combination thereof.
70. The microporous membrane of claim 60, wherein the microporous
membrane comprises a penta-layered membrane comprising a structure
of PP/PE/PP/PE/PP, where PP is a polypropylene, a polypropylene
blend, a polypropylene copolymer, or any combination thereof, and
PE is a polyethylene, a polyethylene blend, a polyethylene
copolymer, or any combination thereof.
71. The microporous membrane of claim 70, wherein each of the five
layers (inner or outer) of the penta-layered membrane is laminated
to their respective adjacent layers (inner or outer).
72. The microporous membrane of claim 60, wherein: each layer
(inner or outer) comprises two, three, four, five, or more
sublayers. each layer (inner or outer) comprises two, three, or
more sublayers; each layer (inner or outer) comprises three
sublayers; each layer (inner or outer) comprises three sublayers,
wherein each sublayer has a maximum average thickness of 6 .mu.m or
less, 5 .mu.m or less, 4 .mu.m or less, 3 .mu.m or less, 2 .mu.m or
less, or 1 .quadrature.m or less; the membrane has a maximum
average thickness ranging from 1 to 50 microns each layer comprises
a maximum average thickness of 33%, 32%, 31%, 30%, 29%, 28%, or
less that 28% of a total average thickness of the membrane; the
membrane has been machine direction stretched; the membrane has
been transverse direction stretched; the membrane has been machine
direction stretched and transverse direction stretched; the
microporous membrane has been transverse direction stretched and
calendered; the membrane further comprises an additive; the
membrane further comprises an additive, wherein the additive
comprises a functionalized polymer, an ionomer, a cellulose
nanofiber, an inorganic particle, a lubricating agent, a nucleating
agent, a cavitation promoter, a fluoropolymer, a cross-linker, a
x-ray detectable material, a polymer processing agent, a high
temperature melt index (NTMI) polymer, an electrolyte additive, an
energy dissipative non-miscible additive, or any combination
thereof; or the membrane comprises an additive, wherein the
additive is a coating on the first outer layer, the second outer
layer, or both the first and second layers.
73. The microporous membrane of claim 72, wherein each of the
sublayers is coextruded, an optionally wherein each layer has a
maximum average thickness of 1.2 mil or less, 1.1 mil or less, 1
mil or less, or 0.9 mil or less 0.8 mil or less, 0.75 mil or less,
0.5 mil or less, 0.4 mil or less, 0.3 mil or less, or 0.2 mil or
less prior to stretching.
74. The microporous membrane of claim 68, wherein: the first and
second outer layers and the second inner (or middle) layer have an
average polypropylene pore size in the range of 0.02 and 0.06
.mu.m; or the first and third inner layers have an average
polyethylene pore size in the range of 0.03 to 1.0 .mu.m.
75. The microporous membrane of claim 60, wherein: the membrane has
an increased or improved elasticity at or above 150.degree. C.
compared to a PP/PE/PP tri-layer microporous membrane having the
same thickness, Gurley, porosity, and/or layer composition make-up
as the membrane; the membrane has an increased or improved puncture
resistance compared to a PP/PE/PP tri-layer microporous membrane
having the same thickness, Gurley, porosity, and/or layer
composition make-up as the membrane; the membrane has an increased
or improved machine direction tensile at break compared to a
PP/PE/PP tri-layer microporous membrane having the same thickness,
Gurley, porosity, and/or layer composition make-up as the membrane;
or the membrane has an increased or improved TD elongation compared
to a PP/PE/PP tri-layer microporous membrane having the same
thickness, Gurley, porosity, and/or layer composition make-up as
the membrane.
76. In a lithium ion battery, a device, or a textile, the
improvement comprising the microporous membrane of claim 60.
77. A method of making a multilayer microporous membrane, the
method comprising: extruding a polypropylene precursor comprising a
plurality of sublayers; extruding a polyethylene precursor
comprising a plurality of sublayers; laminating the extruded
polypropylene precursor layers with the extruded polyethylene
precursor layers to form a first intermediate precursor having an
alternating polyethylene and polypropylene precursors structure;
simultaneously or singly laminating a first outer layer comprising
one of the extruded polypropylene precursors to a first surface of
the intermediate precursor and a second outer layer comprising one
of the extruded polypropylene precursors to a second surface of the
first intermediate precursor opposite the first surface to form a
second intermediate precursor; annealing the second intermediate
precursor to form an annealed multilayer membrane; stretching the
annealed multilayer membrane to form a microporous multilayer
membrane, wherein the stretching is uniaxial or biaxial; and
optionally calendering the microporous multilayer membrane.
78. The method of claim 77, wherein: the first intermediate
precursor comprises a trilayer structure of PE/PP/PE or PP/PE/PP or
a four-layer structure of PP/PE/PE/PP or PE/PP/PP/PE; the second
intermediate precursor comprises a penta-layer structure of
PP/PE/PP/PE/PP or PE/PP/PE/PP/PE or a six-layer structure of
PP/PP/PE/PE/PP/PP, PE/PE/PP/PP/PE/PE, PP/PE/PE/PE/PE/PP, or
PE/PP/PP/PP/PP/PE; the uniaxial stretching is in the machine
direction or the transverse direction; the biaxial stretching is in
the machine direction and transverse direction; the biaxial
stretching is in the machine direction and transverse direction,
wherein the machine direction and transverse direction stretching
is sequential or simultaneous; the extruded polypropylene precursor
comprises two, three, four, or more sublayers; the extruded
polyethylene precursor comprises two, three, four, or more
sublayers; the second intermediate precursor comprises a
penta-layer structure of PP/PE/PP/PE/PP, where each of the
polyethylene and polypropylene precursors comprises three
sublayers; or the extruded polypropylene precursor and the extruded
polyethylene precursor are nonporous.
79. The method of claim 78, further comprising the step of coating
one or more of the first outer layer and the second outer
layer.
80. A method for making a penta-layer microporous membrane
comprising: extruding a plurality of polypropylene membranes and
polyethylene membranes; laminating one of the polyethylene
membranes to a first side of a polypropylene membrane and another
one of the polyethylene membranes to an opposite second side of the
polypropylene membrane to form an inverted trilayer membrane having
a structure of PE/PP/PE; simultaneously or singly laminating one of
the polypropylene layers to one of the polyethylene membranes in
the inverted trilayer membrane and another of the polypropylene
layers to the other polyethylene membrane in the inverted trilayer
membrane to form a penta-layer membrane having a structure of
PP/PE/PP/PE/PP; annealing the penta-layer membrane; and stretching
the annealed penta-layer membrane to form the microporous membrane,
wherein the stretching is uniaxial or biaxial or stretching and
optionally calendering the annealed penta-layer membrane to form
the microporous multilayer membrane.
81. A battery separator, a lithium ion battery separator, a device,
or a textile comprising the microporous membrane formed by the
method of claim 78.
82. A multilayer microporous membrane comprising three or more
lamination interfaces and exhibiting a puncture strength of 150 g
or more 260 g or more, 270 g or more, 280 g or more, 290 g or more,
300 g or more, 310 g or more, 400 g or more, or 500 g or more.
83. The membrane of claim 82, comprising three lamination
interfaces; comprising four lamination surfaces; or comprising five
or more lamination surfaces.
84. The membrane of claim 82, wherein the membrane comprises four
or more layers, each layer comprising two or more sublayers formed
by a co-extrusion process.
85. In a electrochemical cell, battery, capacitor, super capacitor,
double layer super capacitor, fuel cell, lithium battery, lithium
ion battery, secondary lithium battery, and/or secondary lithium
ion battery the improvement comprising the microporous membrane of
claim 60.
Description
[0001] This Application is a 371 Application which claims priority
to PCT/US2019/051210, filed Sep. 16, 2019, which claims benefit of
and priority to U.S. Provisional Patent Application No. 62/732,089,
filed Sep. 17, 2018, and is hereby incorporated by reference herein
in its entirety.
FIELD
[0002] In accordance with at least selected embodiments, the
application, disclosure or invention relates to new or improved
membranes, separator membranes, separators, battery separators,
secondary lithium battery separators, multilayer membranes,
multilayer separator membranes, multilayer separators, multilayer
battery separators, multilayer secondary lithium battery
separators, multilayer battery separators, batteries, capacitors,
fuel cells, lithium batteries, lithium ion batteries, secondary
lithium batteries, and/or secondary lithium ion batteries, and/or
methods for making and/or using such membranes, separator
membranes, separators, battery separators, secondary lithium
battery separators, batteries, capacitors, fuel cells, lithium
batteries, lithium ion batteries, secondary lithium batteries,
and/or secondary lithium ion batteries, and/or devices, vehicles or
products including the same, and/or methods for testing,
quantifying, characterizing, and/or analyzing such membranes,
separator membranes, separators, battery separators, and the like.
In accordance with at least certain embodiments, the disclosure or
invention relates to membrane layers, membranes or separator
membranes, battery separators including such membranes, and/or
related methods. In accordance with at least certain selected
embodiments, the disclosure or invention relates to porous polymer
membranes or separator membranes, battery separators including such
membranes, and/or related methods. In accordance with at least
particular embodiments, the disclosure or invention relates to
microporous polyolefin membranes or separator membranes, microlayer
membranes, multi-layer membranes including one or more microlayer
or nanolayer membranes, battery separators including such
membranes, and/or related methods. In accordance with at least
certain particular embodiments, the disclosure or invention relates
to microporous stretched polymer membranes or separator membranes
having one or more exterior layers and/or interior layers,
microlayer membranes, multi-layered microporous membranes or
separator membranes having exterior layers and interior layers,
some of which layers or sublayers are created by co-extrusion and
then laminated together to form the membranes or separator
membranes. In some embodiments, certain layers, microlayers or
nanolayers can comprise a homopolymer, a copolymer, block
copolymer, elastomer, and/or a polymer blend. In select
embodiments, at least certain layers, microlayers or nanolayers can
comprise a different or distinct polymer, homopolymer, copolymer,
block copolymer, elastomer, and/or polymer blend. The disclosure or
invention also relates to methods for making such a membrane,
separator membrane, or separator, and/or methods for using such a
membrane, separator membrane or separator, for example as a lithium
battery separator. In accordance with at least selected
embodiments, the application or invention is directed to
multi-layered and/or microlayer porous or microporous membranes,
separator membranes, separators, composites, electrochemical
devices, and/or batteries, and/or methods of making and/or using
such membranes, separators, composites, devices and/or batteries.
In accordance with at least particular selected embodiments, the
application or invention is directed to separator membranes that
are multi-layered, in which one or more layers of the multi-layered
structure is produced in a multi-layer or microlayer co-extrusion
die with multiple extruders. The membranes, separator membranes, or
separators can demonstrate improved shutdown, improved strength,
improved dielectric breakdown strength, and/or reduced tendency to
split.
BACKGROUND
[0003] Many batteries, such as lithium ion batteries, incorporate
monolayer or multilayer (two plus layers) membrane separators to
separate electrodes, retain electrolyte, enhance charge transfer,
and other roles. One conventional separator membrane design is a
trilayer polyolefin-based separator by Celgard, LLC of Charlotte,
N.C. While these conventional trilayer designs have been effective
in many lithium and other batteries, especially in secondary
lithium ion batteries, they may not work as effectively in certain
newer battery designs, because in certain battery technologies they
may not fully optimize a balance of strength and/or performance
properties for use in newer applications of certain primary and/or
secondary batteries, such as lithium ion rechargeable batteries.
This is especially true as the battery separator requirements are
becoming more demanding as customers want thinner and stronger
battery separators. For example, a microporous trilayer membrane
formed by coextruding the three layers can in some instances have
reduced strength when made at thinner specifications. Separators
formed by laminating monolayers can also in some instances fail to
satisfy the ever-increasing demands of the new thinner and stronger
separators in certain new applications.
[0004] Hence, there is a need for a new and improved multi-layered
microporous membranes, base films, or battery separators having
various improvements over prior or typical membranes, base films,
or battery separators.
SUMMARY
[0005] In accordance with at least selected embodiments, the
application, disclosure or invention may address the prior needs,
issues or problems, and may provide new or improved membranes,
separator membranes, separators, battery separators, secondary
lithium battery separators, multilayer (or multi-layer) membranes,
multilayer separator membranes, multilayer separators, multilayer
battery separators, multilayer secondary lithium battery
separators, multilayer battery separators, batteries, capacitors,
super capacitors, double layer super capacitors, fuel cells,
lithium batteries, lithium ion batteries, secondary lithium
batteries, and/or secondary lithium ion batteries, and/or methods
for making and/or using such membranes, separator membranes,
separators, battery separators, secondary lithium battery
separators, batteries, capacitors, fuel cells, lithium batteries,
lithium ion batteries, secondary lithium batteries, and/or
secondary lithium ion batteries, and/or devices, vehicles or
products including the same, and/or methods for testing,
quantifying, characterizing, and/or analyzing such membranes,
separator membranes, separators, battery separators, and the like.
In accordance with at least certain embodiments, the disclosure or
invention relates to membrane layers, membranes or separator
membranes, battery separators including such membranes, and/or
related methods. In accordance with at least certain selected
embodiments, the disclosure or invention relates to porous polymer
membranes or separator membranes, battery separators including such
membranes, and/or related methods. In accordance with at least
particular embodiments, the disclosure or invention relates to
microporous polyolefin membranes or separator membranes, microlayer
membranes, multi-layer membranes including one or more microlayer
or nanolayer membranes, battery separators including such
membranes, and/or related methods. In accordance with at least
certain particular embodiments, the disclosure or invention relates
to microporous stretched polymer membranes or separator membranes
having one or more exterior layers and/or interior layers,
microlayer membranes, multi-layered microporous membranes or
separator membranes having exterior layers and interior layers,
some of which layers or sublayers are created by co-extrusion and
then laminated together to form the membranes or separator
membranes. In some embodiments, certain layers, microlayers or
nanolayers can comprise a homopolymer, a copolymer, block
copolymer, elastomer, and/or a polymer blend. In select
embodiments, at least certain layers, microlayers or nanolayers can
comprise a different or distinct polymer, homopolymer, copolymer,
block copolymer, elastomer, and/or polymer blend. The disclosure or
invention also relates to methods for making such a membrane,
separator membrane, or separator, and/or methods for using such a
membrane, separator membrane or separator, for example as a lithium
battery separator. In accordance with at least selected
embodiments, the application or invention is directed to
multi-layered and/or microlayer porous or microporous membranes,
separator membranes, separators, composites, electrochemical
devices, and/or batteries, and/or methods of making and/or using
such membranes, separators, composites, devices and/or batteries.
In accordance with at least particular selected embodiments, the
application or invention is directed to separator membranes that
are multi-layered, in which one or more layers of the multi-layered
structure is produced in a multi-layer or microlayer co-extrusion
die, e.g., a co-extrusion die with multiple extruders. The
membranes, separator membranes, or separators can demonstrate
improved shutdown, improved strength, improved dielectric breakdown
strength, and/or reduced tendency to split.
[0006] In an aspect, a membrane described herein is a multilayered
membrane. In some instances, the multilayered membrane comprises
two outer layers, each outer layer comprising a polyolefin; and two
or more inner layers, each inner layer comprising a polyolefin;
wherein each of the outer layers is laminated to one inner layer
and each of the two or more inner layers is laminated to at least
one of the other inner layers. The polyolefin composition of each
of the outer layers can comprise a polypropylene, a polypropylene
blend, a polypropylene copolymer, a polyethylene, a polyethylene
blend, a polyethylene copolymer, or any combination thereof. In
some embodiments, the polyolefin composition of the outer layer
comprises a polypropylene, a polypropylene blend, a polypropylene
copolymer, or any combination thereof. In some embodiments, the
polyolefin composition of each of the inner layers can comprise a
polypropylene, a polypropylene blend, a polypropylene copolymer, a
polyethylene, a polyethylene blend, a polyethylene copolymer, or
any combination thereof.
[0007] In some instances, the two or more inner layers comprises a
plurality of inner layers, such as two, three, four, five, six, or
more inner layers. In some cases, the plurality of inner layers
comprises two, three, or more layers. In one particular embodiment,
the plurality of inner layers comprises three layers. In another
embodiment, there are four inner layers, or five inner layers, or
six inner layers, or seven inner layers, or eight inner layers, or
nine inner layers, or ten inner layers. In preferred embodiments,
there are two or more, or three or more inner layers so that 3 or
more or four or more lamination interfaces are formed when the
inner and outer layers are laminated together to form the
microporous membrane.
[0008] Some new and improved multi-layered microporous membranes
have been disclosed in, for example, WO 2017/083633, but as the
industry becomes more demanding, even better products than these
may be needed. The disclosure of WO 2017/083633 is incorporated by
reference herein in its entirety.
[0009] The microporous membrane can in some instances be a
penta-layered membrane comprising a first outer layer, a first
inner layer, a second inner (or middle layer), a third inner layer,
and a second outer layer. The first outer layer can be laminated to
the first inner layer, the first inner layer can be laminated to
the second inner (or middle) layer, the second inner (or middle)
layer can be laminated to the third inner layer, and the third
inner can be laminated to the second outer layer, forming four
lamination interfaces between the five layers. The composition of
the first and second outer layers and the second inner (or middle)
layer can comprise a polypropylene, a polypropylene blend, a
polypropylene copolymer, or any combination thereof. The
composition of the first and second inner layers can comprise a
polyethylene, a polyethylene blend, a polyethylene copolymer, or
any combination thereof. In some embodiments, these layers may
comprise a polyethylene, a polyethylene blend, a polyethylene
copolymer, or any combination thereof.
[0010] In some embodiments, a multilayer membrane described herein
comprises a penta-layered membrane comprising a structure of
PP/PE/PP/PE/PP, where PP is a polypropylene, a polypropylene blend,
a polypropylene copolymer, or any combination thereof, and PE is a
polyethylene, a polyethylene blend, a polyethylene copolymer, or
any combination thereof. In some instances, each of these
penta-layers is laminated to their respective adjacent layers.
[0011] In some preferred embodiments, each of the layers in the
multilayer membrane can comprise two, three, four, five, or six, or
seven, or eight, or nine, or more sublayers. In some preferred
instances, each layer comprises two, three, or more sublayers, and
in some preferred instances, each layer comprises three sublayers.
In some preferred embodiments, each of the sublayers of a layer can
be coextruded together. Each sublayer can have a maximum average
thickness of 6 .mu.m or less, 5 .mu.m or less, 4 .mu.m or less, 3
.mu.m or less, or 2 .mu.m or less, or 1 .mu.m or less.
[0012] In some instances, each layer in the multilayer membrane can
have a maximum average thickness prior to stretching. For example,
in some instances, each layer in the multilayer membrane can have a
maximum average thickness of 1.2 mil or less, 1.1 mil or less, 1
mil or less, or 0.9 mil or less 0.8 mil or less, 0.75 mil or less,
0.5 mil or less, 0.4 mil or less, 0.3 mil or less, or 0.2 mil or
less prior to stretching. Based on the number of layers in the
multilayered membrane, the membrane as a maximum average thickness
ranging from 1 to 50 microns. Each layer in the multilayer membrane
can have a maximum average thickness of 33% or less, 32% or less,
31% or less, 30% or less, 29% or less, 28% or less, 27% or less,
26% or less, 25% or less, 24% or less, 23% or less, 22% or less,
21% or less, 20% or less, 19% or less, 18% or less, or 17% or less
or less than a total average thickness of the membrane.
[0013] The laminated multilayer membrane can in some instances be
uniaxially or biaxially stretched. In some embodiments, the
multilayered membrane can be machine direction (MD) stretched,
transverse direction (TD) stretched, or both MD and TD stretched.
When the multilayered membrane is both MD and TD stretched, the
stretching can be sequential or simultaneous. Moreover, in some
instances the multilayered membrane can be calendered after
stretching, such as being calendered after TD stretching.
[0014] In some embodiments, the multilayered membrane can comprise
an additive, such as a functionalized polymer, an ionomer, a
cellulose nanofiber, an inorganic particle, a lubricating agent, a
nucleating agent, a cavitation promoter, a fluoropolymer, a
cross-linker, a x-ray detectable material, a polymer processing
agent, a high temperature melt index (HTMI) polymer, an electrolyte
additive, an energy dissipative non-miscible additive, or any
combination thereof. The additive can be part of a coating on the
first outer layer, the second outer layer, or both layers. In some
embodiments, the additive may be incorporated into one or more of
the outer layers. When the outer layers comprise two or more
sublayers, the additive may be incorporated into any one, some, or
all of the sublayers.
[0015] In some embodiments, the multilayered membrane is a
microporous multilayered membrane. In some instances, the first and
second outer layers and the second inner (or middle) layer can have
an average polypropylene pore size in the range of 0.01 to 1.0
microns and in some instances from 0.02 and 0.06 .mu.m. In some
instances, the first and third inner layers can have an average
polyethylene pore size in the range of 0.01 to 1.0 microns and in
some instances from 0.03 to 0.1 .mu.m. Pore size may be measured
using, for example, Aquapore or a water or mercury intrusion
methodology.
[0016] The multilayered membrane can show improved physical
properties compared to a similar tri-layer membrane. For example,
in some embodiments, the multilayered membrane can have an
increased or improved elasticity at or above 150.degree. C.
compared to, for example, a PP/PE/PP tri-layer microporous membrane
or a (PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) multilayer "trilayer"
microporous membrane having the same thickness, Gurley, porosity,
and/or layer composition make-up as the membrane. In some
embodiments, the multilayered membrane can have an increased or
improved puncture resistance compared to, for example, a PP/PE/PP
tri-layer microporous membrane or a
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) multilayer "trilayer" microporous
membrane having the same thickness, Gurley, porosity, and/or layer
composition make-up as the membrane. The membrane has an increased
or improved machine direction tensile at break compared to, for
example, a PP/PE/PP tri-layer microporous membrane or a
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) multilayer "trilayer" microporous
membrane having the same thickness, Gurley, porosity, and/or layer
composition make-up as the membrane. In some instances, the
multilayered membrane has an increased or improved TD elongation
compared to, for example, a PP/PE/PP tri-layer microporous membrane
or a (PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) multilayer "trilayer"
microporous membrane having the same thickness, Gurley, porosity,
and/or layer composition make-up as the membrane.
[0017] In some instances for a lithium ion battery, an improvement
comprises a multilayered membrane described herein. In a device, an
improvement in some cases comprises a multilayered membrane
described herein. In a textile, an improvement in some instances
comprises a multilayered membrane described herein.
[0018] In another embodiment, a method of making a multilayer
microporous membrane is described herein. The method comprises
extruding a nonporous polypropylene precursor comprising a
plurality of sublayers; extruding a nonporous polyethylene
precursor comprising a plurality of sublayers; laminating the
extruded polypropylene precursor layers with the extruded
polyethylene precursor layers to form a first intermediate
precursor having polyethylene and/or polypropylene layers, and in
some embodiments, alternating polyethylene and polypropylene
layers; simultaneously or singly/sequentially laminating a first
outer layer comprising the extruded polypropylene or polyethylene
precursors, and in preferred embodiments the polypropylene
precursor, to a first surface of the intermediate precursor and
laminating a second outer layer comprising the extruded
polypropylene precursor or the polyethylene precursor, but in
preferred embodiments the polypropylene precursor, to a second
surface of the first intermediate precursor opposite the first
surface to form a second intermediate precursor; annealing the
second intermediate precursor to form an annealed multilayer
membrane; stretching the annealed multilayer membrane to form a
microporous multilayer membrane, wherein the stretching is uniaxial
or biaxial; and optionally calendering the microporous multilayer
membrane. In some preferred embodiments, calendering is
performed.
[0019] In some embodiments, the extruded polypropylene precursor is
a structure comprising a majority amount of polypropylene and the
extruded polyethylene precursor is a structure comprising a
majority amount of polyethylene. For example, a polypropylene
precursor may have a structure "PP" or (PP/PP) or (PP/PE), or
(PP/PE/PP) or (PP/PE/PP/PP), or (PP/PP/PE/PP/PP) or (PP/PE/PE/PP)
as long as it contains a majority amount of polypropylene. A
polyethylene precursor may have a structure PE (PE/PE), (PP/PE),
(PE/PP/PE), (PE/PP/PP/PE), (PE/PE/PP/PP), etc., as long as it
contains a majority amount of polyethylene. For example, a
polypropylene or polyethylene precursor may have a structure
(PP/PE), but for the polypropylene precursor the PP sublayer may be
thicker than the PE sublayer and for the polyethylene precursor the
PE sublayer may be thicker than the PP sublayer. The thicknesses of
each layer of the precursors may be varied. For example, in some
embodiments, the outer layers may be thinner than the inner layers,
the inner layers may be thinner than the outer layers, the layer
thicknesses may alternate between a thick and a thin, or all the
layers may have different thicknesses.
[0020] In some embodiments, the first intermediate precursor
comprises a trilayer multilayer membrane having a structure of
PE/PP/PE. In some instances, the second intermediate precursor
comprises a penta-layer membrane having a structure of
PP/PE/PP/PE/PP. In each instance, each layer of the trilayer
multilayer structure preferably has two or more sublayers. For
example, PP is (PP/PP/PP), (PP/PE/PP), (PP/PP), or (PP/PE) where
the "PP" is thicker, or a layer comprising three sublayers.
[0021] The uniaxial stretching can be in the machine direction or
the transverse direction, and the biaxial stretching can be in the
machine direction and transverse direction. In instances of biaxial
stretching, the machine direction and transverse direction
stretching can be sequential or simultaneous. In preferred
embodiments, at least MD stretching is done to form pores.
[0022] The extruded precursors can in some instances comprise a
plurality of sublayers. For example, the extruded polypropylene
precursor can in some instances comprise two, three, four, or more
sublayers, and the extruded polyethylene precursor can comprise
two, three, four, or more sublayers. In some embodiments, the
second intermediate precursor can comprise a penta-layer membrane
having a structure of PP/PE/PP/PE/PP, where each layer comprises
three sublayers. This structure is represented by
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) or by
(PP/PE/PP)/(PE/PP/PE)/(PP/PE/PP)/(PE/PP/PE)/(PP/PE/PP) or by, for
example, (PP/PP/PE)/(PE/PP/PE)/(PE/PP/PE)/(PE/PP/PE)/(PE/PP/PP). In
the second structure or the third structure, PP or PE may be the
majority polymer in either of (PP/PE/PP) or (PE/PP/PE) or
(PP/PE/PE) or (PE/PE/PP).
[0023] In some embodiments, the extruded polypropylene precursor
and the polyethylene precursor are nonporous. Micropores can in
some instances be formed in the uniaxial or biaxial stretching
step. In preferred embodiments, pores or micropores may be formed
in at least the MD stretching step of a uniaxial or biaxial
process. In some cases, the method can further comprise a step of
coating one or more of the first outer layer and the second outer
layer.
[0024] In another aspect, a method for making a penta-layer
microporous membrane is described herein comprising extruding a
plurality of polypropylene membranes and polyethylene membranes;
laminating one of the polyethylene membranes to a first side of a
polypropylene membrane and another one of the polyethylene
membranes to an opposite second side of the polypropylene membrane
to form an inverted trilayer multilayer membrane having a structure
of PE/PP/PE or (PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE) laminating one of
the polypropylene layers to one of the polyethylene membranes in
the inverted trilayer multilayer membrane and another of the
polypropylene layers to the other polyethylene membrane in the
inverted trilayer multilayer membrane to form a penta-layer
multilayer membrane having a structure of PP/PE/PP/PE/PP or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP); annealing
the penta-layer multilayer membrane; stretching the annealed
multilayer membrane to form a microporous multilayer membrane,
wherein the stretching is uniaxial or biaxial; and optionally
calendering the microporous multilayer membrane. In some preferred
embodiments, the stretching is biaxial. In some preferred
embodiments,
[0025] In an embodiment, the microporous membrane made by the
methods described herein comprises a battery separator. In some
instances, the microporous membrane made by the methods described
herein comprises a lithium ion battery separator. In some
instances, the microporous membrane made by the methods described
herein comprises a device. In some instances, the microporous
membrane made by the methods described herein comprises a
textile.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is an SEM of a second pentalayer membrane according
to some embodiments described herein.
[0027] FIG. 2 is an SEM of a second pentalayer membrane according
to some embodiments described herein.
[0028] FIGS. 3a, 3b, and 3c is a schematic drawing of trilayer and
pentalayer membranes according to some embodiments described
herein.
[0029] FIG. 4 is a schematic drawing of trilayers according to some
embodiments described herein.
[0030] FIG. 5 is a schematic drawing of trilayers according to some
embodiments described herein.
[0031] FIG. 6 is a schematic drawing of pentalayers according to
some embodiments described herein.
[0032] FIG. 7 includes SEM images of a first pentalayer described
herein after various processing steps.
[0033] FIG. 8 is a graph showing puncture strength as a function of
In (BW*Thickness) for exemplary membranes described herein.
DETAILED DESCRIPTION
[0034] Embodiments described herein can be understood more readily
by reference to the following detailed description and examples.
Elements, apparatus and methods described herein, however, are not
limited to the specific embodiments presented in the detailed
description and examples. It should be recognized that these
embodiments are merely illustrative of the principles of the
present disclosure. Numerous modifications and adaptations will be
readily apparent to those of skill in the art without departing
from the spirit and scope of the disclosure.
[0035] In addition, all ranges disclosed herein are to be
understood to encompass any and all subranges subsumed therein. For
example, a stated range of "1.0 to 10.0" should be considered to
include any and all subranges beginning with a minimum value of 1.0
or more and ending with a maximum value of 10.0 or less, such as
1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.
[0036] All ranges disclosed herein are also to be considered to
include the end points of the range, unless expressly stated
otherwise. For example, a range of "between 5 and 10," "from 5 to
10," or "5-10" should generally be considered to include the end
points 5 and 10.
[0037] Further, when the phrase "up to" is used in connection with
an amount or quantity, it is to be understood that the amount is at
least a detectable amount or quantity. For example, a material
present in an amount "up to" a specified amount can be present from
a detectable amount and up to and including the specified
amount.
[0038] I. Multilayer Membranes (or Membranes Separators)
[0039] In an aspect, an improved multilayer membrane, membrane, or
separator is disclosed. In some embodiments, a multilayer
microporous membrane, membrane, or separator is disclosed. While
the term "membrane" will be used throughout this specification for
purposes of simplicity, the term should be understood to also refer
to a "membrane" or "separator".
[0040] In some embodiments, the multilayer membrane comprises two
outer layers and a plurality of inner layers. The plurality of
inner layers can comprise 2 or more, 3 or more, 4 or more, 5 or
more, 6 or more, 7 or more, 8 or more, 9 or more 11 or more, 12 or
more, 13 or more, 14 or more, 15 or more, 15 or more, 16 or more 17
or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 or
more, 23 or more, 24 or more, 25 or more, 26 or more, 27 or more,
28 or more, 29 or more, 30 or more, 40 or more, 50 or more, 60 or
more, 70 or more, 80 or more, 90 or more, or 100 or more layers.
The term "layer" comprises a layer having a maximum average
thickness of 0.01 to 2.0, 25, or 3.0 mil prior to being stretched.
In some embodiments, the maximum average thickness is 0.1 to 1.5,
2.0, 2.5, or 3.0 mil prior to being stretched or 0.2 to 1.5, 2.0,
2.5, or 3.0 mil prior to being stretched, or 0.2 to 1.2, 1.5, 2.0,
2.5, or 3.0 mil prior to being stretched. In some preferred
embodiments, the maximum average thickness of the layer is 0.1 to
0.5, 1.0, 1.5, 2.0, 2.5, or 3.0 mil prior to being stretched.
[0041] Each layer can be mono-extruded, where the layer is extruded
by itself, without any sublayers. Alternatively, each layer can
comprise a plurality of co-extruded sublayers. In preferred
embodiments, each layer comprises a plurality, or 2 or more,
co-extruded sublayers. For example, a co-extruded bi-layer (having
two sublayers), tri-layer (having three sublayers), or multi-layer
(having two or more three or more or four or more sublayers)
membrane are each collectively considered to be a "layer". The
number of sublayers in coextruded bi-layer is two, the number of
layers in a co-extruded tri-layer is three, and the number of
layers in a co-extruded multi-layer membrane will be two or more,
three or more, four or more, five or more, and so on. The exact
number of sublayers in a co-extruded layer is dictated by the die
design and not necessarily the materials that are co-extruded to
form the co-extruded layer. For example, a co-extruded bi-, tri-,
or multi-sublayer membrane can be formed using the same material in
each of the two, three, or four or more sublayers, and these
sublayers will still be considered to be separate sublayers even
though each sublayer is made of the same material. Each layer
comprising the co-extruded bi-, tri-, or multi-sublayer membranes
can have a pre-stretched thickness of 3.0 mil or less, 2.5 mil or
less, 2.0 mil or less, 1.5 mil or less, 1.2 mil or less, 1.1 mil or
less, 1 mil or less, or 0.9 mil or less 0.8 mil or less, 0.75 mil
or less, 0.5 mil or less, 0.4 mil or less, 0.3 mil or less, or 0.2
mil or less prior to stretching.
[0042] In some embodiments, the multilayer microporous membrane or
multilayer microporous membrane disclosed herein comprises two,
three, four, or five or more co-extruded layers. Co-extruded layers
are layers formed by a co-extrusion process. In some instances, the
layers can be formed by the same or separate co-extrusion
processes. The consecutive layers can be formed by the same
co-extrusion process, or two or more layers can be coextruded by
one process. Two or layers can be coextruded by a separate process,
and the two or more layers formed by the one process can be
laminated to the two or more layers formed by the separate process
so that combined there are four or more consecutive coextruded
layers. In some embodiments, the co-coextruded layers are formed by
the same co-extrusion process. For example, two or more, or three
or more, four or more, five or more, six or more, seven or more,
eight or more, nine or more, ten or more, fifteen or more, twenty
or more, twenty-five or more, thirty or more, thirty-five or more,
forty or more, forty-five or more, fifty or more, fifty-five or
more or sixty or more co-extruded layers can be formed by the same
co-extrusion process. The extrusion process can also be performed
by extruding two or more polymer mixtures, that can be the same or
different, with or without a solvent. In some instances, the
co-extrusion process is a dry process, such as Celgard.RTM. dry
process, which does not use a solvent.
[0043] In some embodiments, the multilayer membrane described
herein is made by forming a coextruded bi-layer (two coextruded
layers), tri-layer (three coextruded layers), or multi-layer (two,
three, or four or more co-extruded layers) membrane and then
laminating the bi-layer, tri-layer, or multi-layer membrane to at
least one or at least two other membranes. The other membranes can
be a non-woven or woven membrane, mono-extruded membranes, or a
co-extruded membranes. In some preferred embodiments, the other
membranes are co-extruded membranes, including co-extruded
membranes having the same number of co-extruded layers as the
co-extruded bi-layer, tri-layer, or multi-layer membranes.
Moreover, each of the co-extruded layers can comprise two, three,
four, or more sublayers, as previously described herein.
[0044] Lamination of the bi-layer, tri-layer, or multilayer
co-extruded membrane with at least one other monolayer membrane or
a bi-layer, tri-layer, or multi-layer membrane can involve use of
heat, pressure, or heat and pressure.
[0045] The polymers or co-polymers that can be used in the instant
battery separator are those that are extrudable. Such polymers are
typically referred to as thermoplastic polymers.
[0046] In some embodiments, one or more of the layers of the
multilayer microporous membrane or multilayer membrane comprises a
polymer or co-polymer or a polymer or co-polymer blend, a
polyolefin or polyolefin blend. A polyolefin blend, as understood
by one of ordinary skill in the art, can include a mixture of two
or more different kinds of polyolefin, such as polyethylene and
polypropylene, a blend of two or more of the same kind of
polyolefin, wherein each polyolefin has a different property, such
as an ultra-high molecular weight polyolefin and a low or ultra-low
molecular weight polyolefin, or a mixture of a polyolefin and
another type of polymer or co-polymer. An additive, agent, filler,
and/or the like may also be added to the polymers or polymer blends
described herein. For example, an elastomer, a lubricant, an
antioxidant, a colorant, a cross-linker, and/or the like.
[0047] Polyolefins include, but are not limited to: polyethylene,
polypropylene, polybutylene, polymethylpentene, copolymers thereof,
and blends thereof. In some embodiments, the polyolefin can be an
ultra-low molecular weight, a low-molecular weight, a medium
molecular weight, a high molecular weight, or an ultra-high
molecular weight polyolefin, such as a medium or a high weight
polyethylene (PE) or polypropylene (PP). For example, an ultra-high
molecular weight polyolefin can have a molecular weight of 450,000
(450 k) or above, e.g. 500 k or above, 650 k or above, 700 k or
above, 800 k or above, 1 million or above, 2 million or above, 3
million or above, 4 million or above, 5 million or above, 6 million
or above, etc. A high-molecular weight polyolefin can have a
molecular weight in the range of 250 k to 450 k, such as 250 k to
400 k, 250 k to 350 k, or 250 k to 300 k. A medium molecular weight
polyolefin can have a molecular weight from 150 to 250 k, such as
100 k, 125 k, 130 K, 140 k, 150 k to 225 k, 150 k to 200 k, 150 k
to 200 k, etc. A low molecular weight polyolefin can have a
molecular weight in the range of 100 k to 150 k, such as 100 k to
125 k. An ultra-low molecular weight polyolefin can have a
molecular weight less than 100 k. The foregoing values are weight
average molecular weights. In some embodiments, a higher molecular
weight polyolefin can be used to increase strength or other
properties of the microporous multilayer membranes or batteries
comprising the same as described herein. In some embodiments, a
lower molecular weight polymer, such as a medium, low, or ultra-low
molecular weight polymer can be beneficial. For example, without
wishing to be bound by any particular theory, it is believed that
the crystallization behavior of lower molecular weight polyolefins
can result in a microporous multilayer membrane having smaller
pores resulting from at least an MD stretching process that forms
the pores.
[0048] Exemplary thermoplastic polymers, blends, mixtures or
copolymers other than polyolefin polymers, blends, or mixtures can
include, but are not limited to: polyacetals (or
polyoxymethylenes), polyamides, polyesters, polysulfides, polyvinyl
alcohols, polyvinyl esters, and polyvinylidenes, such as
polyvinylidene difluoride (PVDF), Poly(vinylidene
fluoride-co-hexafluoropropylene) (PVDF:HFP),
Polytetrafluoroethylene (PTFE), polyethylene oxide (PEO),
Poly(vinyl alcohol) (PVA), Polyacrylonitrile (PAN), or the like.
Polyamides (nylons) include, but are not limited to: polyamide 6,
polyamide 66, Nylon 10, 10, polyphthalamide (PPA), co-polymers
thereof, and blends thereof. Polyesters include, but are not
limited to: polyester terephthalate, polybutyl terephthalate,
copolymers thereof, and blends thereof. Polysulfides include, but
are not limited to, polyphenyl sulfide, copolymers thereof, and
blends thereof. Polyvinyl alcohols include, but are not limited to:
ethylene-vinyl alcohol, copolymers thereof, and blends thereof.
Polyvinyl esters include, but are not limited to, polyvinyl
acetate, ethylene vinyl acetate, copolymers thereof, and blends
thereof. Polyvinylidenes include, but are not limited to:
fluorinated polyvinylidenes (such as polyvinylidene chloride,
polyvinylidene fluoride), copolymers thereof, and blends thereof.
Various materials can be added to the polymers. These materials are
added, in some instances, to modify or enhance the performance or
properties of an individual layer or the overall membrane. Such
materials include, but are not limited to: Materials to lower the
melting temperature of the polymer can be added. For example, when
the multilayer membrane is a battery separator, the multi-layered
separator includes a layer designed to close its pores at a
predetermined temperature to block the flow of ions between the
electrodes of a battery. This function is commonly referred to as
shutdown.
[0049] In some embodiments, each layer or sublayer of each layer of
the multilayer membrane comprises, consists of, or consists
essentially of a different polymer or co-polymer or polymer or
co-polymer blend. In some embodiments each layer comprises,
consists of, or consists essentially of the same polymer or
co-polymer or polymer or co-polymer blend. In some embodiments,
alternating layers of the multilayer microporous membrane or the
multilayer membrane comprise, consist of, or consist essentially of
the same polymer or co-polymer or polymer or co-polymer blend. In
other embodiments, some of the layers and/or sublayers of the
multilayer membrane or microporous multilayer membrane comprise,
consist of, or consist essentially of the same polymer or polymer
blend and some do not.
[0050] In some embodiments, the layers or sublayers of the
multilayer membrane comprise, consist of, or consist essentially of
polyolefin (PO) such as PP or PE or PE+PP blends, mixtures,
co-polymers, or the like, and further comprise other polymers (PY),
additives, agents, materials, fillers, and/or particles (M), and/or
the like can be added or used and can form layers or microlayers
such as PP+PY, PE+PY, PP+M, PE+M, PP+PE+PY, PE+PP+M, PP+PY+M,
PE+PY+M, PP+PE+PY+M, or blends, mixtures, co-polymers, and/or the
like thereof.
[0051] Identical, similar, distinct, or different PP or PE or PE+PP
polymers, homopolymers, copolymers, molecular weights, blends,
mixtures, co-polymers, or the like can also be used. For example,
identical, similar, distinct, or different molecular weight PP, PE,
and/or PP+PE polymers, homopolymers, co-polymers, multi-polymers,
blends, mixtures, and/or the like can be used in each layer or
sublayers. As such, constructions can include various combinations
and subcombinations of PP, PE, PP+PE, PP1, PP2, PP3, PE1, PE2, PE3,
PP1+PP2, PE1+PE2, PP1+PP2+PP3, PE1+PE2+PE3, PP1+PP2+PE, PP+PE1+PE2,
PP1/PP2, PP1/PP2/PP1, PE1/PE2, PE1/PE2/PP1, PE1/PE2/PE3,
PP1+PE/PP2, or other combinations or constructions.
[0052] In some embodiments, one or more additives can be added to
the outermost layers of the multilayer microporous membrane or the
multilayer membrane to improve the properties thereof or the
properties of the battery separator or battery comprising the same.
The outermost layer or any sublayer, including the outermost
sublayer, of the outermost layer can comprise PE, PP, or PE+PP in
addition to the additive. For example, to improve pin removal
(i.e., lower the coefficient of friction of the membrane or
membrane), additives such as lithium stearate, calcium stearate, PE
beads, siloxane, and polysiloxanes can be added.
[0053] In addition, particular polymers, co-polymer or polymer or
co-polymer blends can be used in the outermost layers (such as a
first outer layer and a second outer layer or the outermost
sublayer or any other sublayer of these first and second outer
layers) of the multilayer membrane to improve the properties
thereof or the properties of a battery separator or battery
comprising the same. For example, adding an ultra-high molecular
weight polymer or co-polymer in the outermost layer can improve
puncture strength.
[0054] In further embodiments additives to improve oxidation
resistance can be added to the outermost layers of the multilayer
microporous membrane or membranes. The additive can be an organic
or inorganic additive or a polymeric or non-polymeric additive.
[0055] In some embodiments, the outermost layers of the multilayer
membrane or membrane can comprise, consist of, or consist
essentially of polyethylene, polypropylene, or a mixture
thereof.
[0056] As described above, the multilayer membrane can comprise two
outer layers (a first outer layer and a second outer layer) and a
plurality of inner layers. The plurality of inner layers can be
mono-extruded or co-extruded layers. A lamination barrier or
interface can be formed between each of the inner layers and/or
between each of the outer layers and one of the inner layers. A
lamination barrier or interface is formed when two surfaces, such
as two surfaces of different membranes or layers are laminated
together using heat, pressure, or heat and pressure. In some
embodiments, the layers of the membrane areas have the following
non-limiting constructions: PP, PE, PP/PP, PP/PE, PE/PP, PE/PE,
PP/PP/PP, PP/PP/PE, PP/PE/PE. PP/PE/PP, PE/PP/PE, PE/PE/PP,
PP/PP/PP/PP, PP/PE/PE/PP, PE/PP/PP/PE, PP/PE/PP/PP, PE/PE/PP/PP,
PE/PP/PE/PP, PP/PE/PE/PE/PP, PE/PP/PP/PP/PE, PP/PP/PE/PP/PP,
PE/PE/PP/PP/PE/PE, PP/PE/PP/PE/PP, PP/PP/PE/PE/PP/PP,
PE/PE/PP/PP/PE/PE, PE/PP/PE/PP/PE/PP, PP/PE/PP/PE/PP/PE,
PP/PP/PP/PE/PP/PP/PP, PE/PE/PE/PP/PE/PE/PE, PP/PE/PP/PE/PP/PE/PP,
PE/PP/PE/PP/PE/PP/PE, PE/PP/PE/PP/PE/PP/PE/PP,
PP/PE/PP/PE/PP/PE/PP/PE, PP/PP/PE/PE/PP/PP/PE/PE,
PP/PE/PE/PE/PE/PE/PE/PP, PE/PP/PP/PP/PP/PP/PP/PE,
PP/PP/PE/PE/PEPE/PP/PP, PP/PP/PP/PP/PE/PE/PE/PE,
PP/PP/PP/PP/PE/PP/PP/PP/PP, PE/PE/PE/PE/PP/PE/PE/PE/PE,
PP/PE/PP/PE/PP/PE/PP/PE/PP, PE/PP/PE/PP/PE/PP/PE/PP/PE,
PE/PE/PE/PE/PE/PP/PP/PP/PP, PP/PP/PP/PP/PP/PE/PE/PE/PE,
PP/PP/PP/PP/PP/PE/PE/PE/PE/PE, PE/PE/PE/PE/PE/PP/PP/PP/PP/PP,
PP/PE/PP/PE/PP/PE/PP/PE/PP/PE, PE/PP/PE/PP/PE/PP/PE/PP/PE/PP,
PE/PP/PP/PP/PP/PP/PP/PP/PP/PP/PE, PP/PE/PE/PE/PE/PE/PE/PE/PE/PE/PP,
PP/PP/PE/PE/PP/PP/PE/PE/PP/PP, PE/PE/PP/PP/PP/PP/PP/PP/PP/PE/PE,
PP/PP/PP/PE/PE/PP/PP/PP/PP/PE, PE/PE/PE/PP/PP/PE/PE/PE/PP/PP. For
purposes of reference herein PE denotes a single layer (which in
preferred embodiments includes sublayers) within the multilayer
membrane that comprises, consists of, or consists essentially of
PE. Similarly, PP denotes a single layer (which in preferred
embodiments includes sublayers) within the multilayer membrane that
comprises, consists of, or consists essentially of PP.
[0057] The PE or PP composition in each of the different layers can
be the same or different type of PE or PP compositions in the other
layers. For example, a coextruded precursor can have a structure
(PP1/PP2/PP3), (PP3/PP2/PP1), (PP3/PP3/PP2/PP1/PP1),
(PP3/PP3/PP2/PP2/PP1/PP1), (PP3/PP3/PP3/PP2/PP2/PP2/PP1/PP1/PP1),
and so on. PP1 may be made of a homopolymer PP and an additive to
modify the surface coefficient of friction, including any anti-slip
or anti-block additives like polysiloxane or siloxane. PP2 can be
made of the same or a different PP homopolymer than PP1 and a
copolymer of PP. the PP copolymer can be any propylene-ethylene or
ethylene-propylene random copolymer, block copolymer, or elastomer.
PP3 can be made of the same or a different homopolymer PP than PP1
and PP2 and also includes an additive to modify surface coefficient
of friction, which can be the same or different from that used in
PP1. Stated differently, a multilayer membrane with a general
structure of PP/PE/PP/PE/PP can comprise PP1/PE1/PP2/PE2/PP3, where
each of the PP layers has a different polypropylene composition
than the other two PP layers, and likewise for the two PE
layers.
[0058] In another embodiment, the coextruded precursor can have a
structure (PP1/PP2/PP3), (PP3/PP2/PP1), (PP3/PP3/PP2/PP1/PP1),
(PP3/PP3/PP2/PP2/PP1/PP1), (PP3/PP3/PP3/PP2/PP2/PP2/PP1/PP1/PP1),
and so on. PP1 can be any polypropylene blend. PP2 can be made of
any polypropylene block co-polymer, including those described
herein. PP3 can be made of the same or a different
polypropylene-block co-polymer than that used in PP2.
[0059] The individual layers in the multilayer membrane can
comprise a plurality of sublayers, which can be formed by
co-extrusion or combining, e.g., by lamination, the individual
mono-extruded sublayers to form the individual layer of the
multilayer membrane. Using a multilayer membrane having a structure
of PP/PE/PP/PE/PP, each individual PP or PE layer can comprise two
or more co-extruded sublayers. For example, when each individual PP
or PE layer comprises three sublayers, each individual PP layer can
be expressed as PP=(PP1,PP2,PP3) and each individual PE layer can
be expressed as PE=(PE1,PE2,PE3). Thus, the structure of
PP/PE/PP/PE/PP can be expressed as
(PP1,PP2,PP3)/(PE1,PE2,PE3)/(PP1,PP2,PP3)/(PE1,PE2,PE3)/(PP1,PP2,PP3)
or as
(PP1/PP2/PP3)/(PE1/PE2/PE3)/(PP1/PP2/PP3)/(PE1/PE2/PE3)/(PP1/PP2/PP3).
The composition of each of the PP1, PP2, and PP3 sublayers can be
the same, or each sublayer can have a different polypropylene
composition than one or both of the other polypropylene sublayers.
Similarly, composition of each of the PE1, PE2, and PE3 sublayers
can be the same, or each sublayer can have a different polyethylene
composition than one or both of the other polyethylene sublayers.
This principle applies to other multilayer membranes having more or
less layers that the above-described exemplary penta-layer
membrane. The improved or inventive penta-layer multilayer membrane
described above has four lamination interfaces. A similar six-layer
multilayer membrane would have 5 lamination interfaces and a
similar four layer multilayer membrane would have three lamination
surfaces. It is hypothesized herein that a multilayer membrane
having 3 or more, and in some preferred embodiments 4 or more
lamination interfaces, will have improved properties. For example
they will have improved properties compared to certain microlayer
three layer (or trilayer) multilayer membranes that have only two
lamination interfaces or compared to a traditional trilayer.
[0060] The maximum average thickness of each sublayer in a layer
can less than 50 microns, less than 40 microns, less than 30
microns, less than 25 microns, less than 20 microns, less than 19
microns, less than 18 microns, less than 17 microns, less than 16
microns, less than 15 microns, less than 14 microns, less than 13
microns, less than 12 microns, less than 11 microns, less than 10
microns, less than 9 microns, less than 8 microns, less than 7
microns, less than 6 microns, less than 5 microns, less than 4
microns, less than 3 microns, less than 2 microns, or less than 1
micron. The thickness of each layer of the microporous membrane can
be 50 microns, less than 40 microns, less than 30 microns, less
than 25 microns, less than 20 microns, less than 19 microns, less
than 18 microns, less than 17 microns, less than 16 microns, less
than 15 microns, less than 14 microns, less than 13 microns, less
than 12 microns, less than 11 microns, less than 10 microns, less
than 9 microns, less than 8 microns, less than 7 microns, less than
6 microns, less than 5 microns, less than 4 microns, less than 3
microns, less than 2 microns, or less than 1 micron. The thickness
of the microporous membrane can be 50 microns, less than 40
microns, less than 30 microns, less than 25 microns, less than 20
microns, less than 19 microns, less than 18 microns, less than 17
microns, less than 16 microns, less than 15 microns, less than 14
microns, less than 13 microns, less than 12 microns, less than 11
microns, less than 10 microns, less than 9 microns, less than 8
microns, less than 7 microns, less than 6 microns, less than 5
microns, less than 4 microns, less than 3 microns, less than 2
microns, or less than 1 micron. This is the thickness of the
multilayer membranes or membranes before any coating or treatment
is applied thereto.
[0061] Microporous as used herein means that the average pore size
of the membrane, or coating is 2 microns or less, 1 micron or less,
0.9 microns or less, 0.8 microns or less, 0.7 microns or less, 0.6
microns or less, 0.5 microns or less, 0.4 microns or less, 0.3
microns or less, 0.2 microns or less, and 0.1 microns or less, 0.09
microns or less, 0.08 microns or less, 0.07 microns or less, 0.06
microns or less, 0.05 microns or less, 0.04 microns or less, 0.03
microns or less, 0.02 microns or less, or 0.01 microns or less. In
some embodiments, pores can be formed, for example, by performing a
stretching process on a precursor membrane, such as is done in the
Celgard.RTM. dry process.
[0062] In some embodiments, where one or more layers of the
multilayer membrane comprises, consists of, or consists essentially
of microporous PE, the average pore size in the PE layer is between
0.03 and 0.1, between 0.05 to 0.09, 0.05 to 0.08, 0.05 to 0.07, or
0.05 to 0.06.
[0063] In some embodiments, where one or more layers of the
multilayer membrane comprises, consists of, or consists essentially
of microporous PP, the average pore size in the PP layer is between
0.02 to 0.06, 0.03 to 0.05, and more 0.04 to 0.05 or 0.03 to
0.04.
[0064] In instances where the multilayer microporous membrane or
membrane comprises layers comprising, consisting of, or consisting
essentially of PP and comprises other layers comprising, consisting
of, or consisting essentially of PE, the average pore size of the
PP layers is smaller than that of the PE layers.
[0065] The microporous multilayer membrane can have any Gurley not
inconsistent with the objectives of this disclosure, such as a
Gurly that is acceptable for use as a battery separator. In some
embodiments, the microporous multilayer membrane or membrane
described herein has a JIS Gurley (s/100 cc) of 150 or more, 160 or
more, 170 or more, 180 or more, 190 or more, 200 or more, 210 or
more, 220 or more, 230 or more, 240 or more, 250 or more, 260 or
more, 270 or more, 280 or more, 290 or more, 300 or more, 310 or
more, 320 or more, 330 or more, 340 or more, or 350 or more.
Sometimes Gurley may be less than 150 s/100 cc and sometimes it may
be as high as 500 s/100 cc or more. As long as the Gurley allows
the membrane to function as a battery separator, Gurley is not so
limited.
[0066] The porosity of the microporous multilayer membrane can be
any porosity not inconsistent with the goals of this disclosure.
For example, any porosity that could form an acceptable battery
separator is acceptable. In some embodiments, the porosity of the
membrane or membrane can be from 10 to 60%, from 20 to 60%, from 30
to 60%, or from 40 to 60%. Sometimes the porosity of the membrane
may be 65% or more or 70% or more. It is not so limited as long as
the membrane functions as a battery separator.
[0067] The microporous multilayer membrane or membrane can have a
puncture strength, uncoated, of 200 gf or more, 210 gf or more, 220
gf or more, 230 gf or more, 240 gf or more, 250 gf or more, 260 gf
or more, 270 gf or more, 280 gf or more, 290 gf or more, 300 gf or
more, 310 gf or more, 320 gf or more, 330 gf or more, 340 gf or
more, 350 gf or more, or as high as 400 gf or more. In some
embodiments, puncture strength may be lower than 200 gf, especially
for thinner membranes, and in some embodiments, the puncture may be
as high as 500 gf or higher.
[0068] In some embodiments, the multilayer microporous membrane
described herein can comprise one or more additives in at least one
layer of the multilayer microporous membrane. In some embodiments,
at least one layer or sublayer of the multilayer microporous
membranes comprises more than one, such as two, three, four, five,
or more, additives. Additives can be present in one or both of the
outermost layers of the multilayer microporous membrane, in one or
more inner layers, in all of the inner layers, or in all of the
inner and both of the outermost layers. In some embodiments,
additives can be present in one or more outermost layers and in one
or more innermost layers. In such embodiments, over time, the
additive can be released from the outermost layer or layers and the
additive supply of the outermost layer or layers can be replenished
by migration of the additive in the inner layers to the outermost
layers. In some embodiments, each layer of the multilayer
microporous membrane can comprise a different additive or
combination of additives than an adjacent layer or each layer of
the multilayer microporous membrane.
[0069] In some embodiments, the additive is, comprises, consists
of, or consists essentially of a functionalized polymer. As
understood by one of ordinary skill in the art, a functionalized
polymer is a polymer with functional groups coming off of the
polymeric backbone. Exemplary functional groups include: In some
embodiments, the functionalized polymer is a maleic anhydride
functionalized polymer. In some embodiments the maleic anhydride
modified polymer is a maleic anhydride homo-polymer polypropylene,
copolymer polypropylene, high density polypropylene, low-density
polypropylene, ultra-high density polypropylene, ultra-low density
polypropylene, homo-polymer polyethylene, copolymer polyethylene,
high density polyethylene, low-density polyethylene, ultra-high
density polyethylene, ultra-low density polyethylene,
[0070] In some embodiments, the additive comprises, consists of, or
consists essentially of an ionomer. An ionomer, as understood by
one of ordinary skill in the art is a copolymer containing both
ion-containing and non-ionic repeating groups. Sometimes the
ion-containing repeating groups can make up less than 25%, less
than 20%, or less than 15% of the ionomer. In some embodiments, the
ionomer can be a Li-based, Na-based, or Zn-based ionomer.
[0071] In some embodiments, the additives comprises cellulose
nanofiber.
[0072] In some embodiments, the additive comprises inorganic
particles having a narrow size distribution. For example, the
difference between D10 and D90 in a distribution is less than 100
nanometers, less than 90 nanometers, less than 80 nanometers, less
than 70 nanometers, less than 60 nanometers, less than 50
nanometers, less than 40 nanometers, less than 30 nanometers, less
than 20 nanometers, or less than 10 nanometers. In some
embodiments, the inorganic particles are selected from at least one
of SiO.sub.2, TiO.sub.2, or combinations thereof.
[0073] In some embodiments, the additive can comprise, consists of,
or consist essentially of a lubricating agent. The lubricating
agent or lubricant described herein is not so limited. As
understood by one of ordinary skill in the art, a lubricant is a
compound that acts to reduce the frictional force between a variety
of different surfaces, including the following: polymer:polymer;
polymer:metal; polymer; organic material; and polymer:inorganic
material. Specific examples of lubricating agents or lubricants as
described herein are compounds comprising siloxy functional groups,
including siloxanes and polysiloxanes, and fatty acid salts,
including metal stearates.
[0074] Compounds comprising two or more, three or more, four or
more, five or more, six or more, seven or more, eight or more, nine
or more, or ten or more siloxy groups can be used as the lubricant
described herein. Siloxanes, as understood by those in the art, are
a class of molecules with a backbone of alternating silicon atom
(Si) and oxygen (O) atoms, each silicon atom can have a connecting
hydrogen (H) or a saturated or unsaturated organic group, such as
--CH3 or C2H5. Polysiloxanes are a polymerized siloxanes, usually
having a higher molecular weight. In some embodiments described
herein, the polysiloxanes can be high molecular weight, such as
ultra-high molecular weight polysiloxanes. In some embodiments,
high and ultra-high molecular weight polysiloxanes can have weight
average molecular weights ranging from 500,000 to 1,000,000.
[0075] The fatty acid salts described herein are also not so
limited and can be any fatty acid salt that acts as a lubricant.
The fatty acid of the fatty acid salt can be a fatty acid having
between 12 to 22 carbon atoms. For example, the metal fatty acid
can be selected from the group consisting of: Lauric acid, myristic
acid, palmitic acid, stearic acid, oleic acid, linoleic acid,
linolenic acid, palmitoleic acid, behenic acid, erucic acid, and
arachidic acid. The metal can be any metal not inconsistent with
the objectives of this disclosure. In some instances, the metal is
an alkaline or alkaline earth metal, such as Li, Be, Na, Mg, K, Ca,
Rb, Sr, Cs, Ba, Fr, and Ra. In some embodiments, the metal is Li,
Be, Na, Mg, K, or Ca.
[0076] The fatty acid salt can be lithium stearate, sodium
stearate, lithium oleate, sodium oleate, sodium palmitate, lithium
palmitate, potassium stearate, or potassium oleate.
[0077] The lubricant, including the fatty acid salts described
herein, can have a melting point of 200.degree. C. or above,
210.degree. C. or above, 220.degree. C. or above, 230.degree. C. or
above, or 240.degree. C. or above. A fatty acid salt such as
lithium stearate (melting point of 220.degree. C.) or sodium
stearate (melting point 245 to 255.degree. C.) has such a melting
point. A fatty acid salt such as calcium stearate (melting point
155.degree. C.) does not. The inventors of this application have
found that calcium stearate is less ideal, from a processing
standpoint, than other fatty acid metal salts, such as metal
stearates, having higher melting points. Particularly, it has been
found that calcium stearate could not be added in amounts above 800
ppm without what has been termed a "snowing effect" where wax
separates and gets everywhere during a hot extrusion process.
Without wishing to be bound by any particular theory, using a fatty
acid metal salt with a melting point above the hot extrusion
temperatures is believed to solve this "snowing" problem. Fatty
acid salts having higher melting points than calcium stearate,
particularly those with melting points above 200.degree. C., can be
incorporated in amounts above 1% or 1,000 ppm, without "snowing."
Amounts of 1% or above have been found to be important for
achieving desired properties such as improved wettability and pin
removal improvement.
[0078] In some embodiments, the additive can comprise, consist of,
or consist essentially of one or more nucleating agents. As
understood by one of ordinary skill in the art, nucleating agents
are, in some embodiments, materials, inorganic materials, that
assist in, increase, or enhance crystallization of polymers,
including semi-crystalline polymers.
[0079] In some embodiments, the additive can comprise, consist of,
or consist essentially of cavitation promoters. Cavitation
promoters, as understood by those skilled in the art, are materials
that form, assist in formation of, increase formation of, or
enhance the formation of bubbles or voids in the polymer.
[0080] In some embodiments, the additive can comprise, consist of,
or consist essentially of a fluoropolymer. The fluoropolymer is not
so limited and in some embodiments is PVDF.
[0081] In some embodiments, the additive can comprise, consist of,
or consist essentially of a cross-linker.
[0082] In some embodiments, the additive can comprise, consist of,
or consist essentially of an x-ray detectable material. The x-ray
detectable material is not so limited and can be any material, for
example, those disclosed in U.S. Pat. No. 7,662,510, which is
incorporated by reference herein in its entirety. Suitable amounts
of the x-ray detectable material or element are also disclosed in
the '510 patent, but in some embodiments, up to 50 weight %, up to
40 weight %, up to 30 weight %, up to 20 weight %, up to 10 weight
%, up to 5 weight %, or up to 1 weight % based on the total weight
of the microporous membrane or membrane can be used. In an
embodiment, the additive is barium sulfate.
[0083] In some embodiments, the additive can comprise, consist of,
or consist essentially of a lithium halide. The lithium halide can
be lithium chloride, lithium fluoride, lithium bromide, or lithium
iodide. The lithium halide can be lithium iodide, which is both
ionically conductive and electrically insulative. In some
instances, a material that is both ionically conductive and
electrically insulative can be used as part of a battery
separator.
[0084] In some embodiments, the additive can comprise, consist of,
or consist essentially of a polymer processing agent. As understood
by those skilled in the art, polymer processing agents or additives
are added to improve processing efficiency and quality of polymeric
compounds. In some embodiments, the polymer processing agent can be
antioxidants, stabilizers, lubricants, processing aids, nucleating
agents, colorants, antistatic agents, plasticizers, or fillers.
[0085] In some embodiments, the additive can comprise, consist of,
or consist essentially of a high temperature melt index (HTMI)
polymer. The HTMI polymer is not so limited and can be at least one
selected from the group consisting of PMP, PMMA, PET, PVDF, Aramid,
syndiotactic polystyrene, and combinations thereof.
[0086] In some embodiments, the additive can comprise, consist of,
of consist essentially of an electrolyte additive. Electrolyte
additives as described herein are not so limited as long as the
electrolyte is consistent with the stated goals herein. The
electrolyte additive can be any additive typically added by battery
makers, particularly lithium battery makers to improve battery
performance. Electrolyte additives preferably should also be
capable of being combined, such as miscible, with the polymers used
for the polymeric microporous membrane or compatible with the
coating slurry. Miscibility of the additives can also be assisted
or improved by coating or partially coating the additives. For
example, exemplary electrolyte additives are disclosed in A Review
of Electrolyte Additives for Lithium-Ion Batteries, J. of Power
Sources, vol. 162, issue 2, 2006 pp. 1379-1394, which is
incorporated by reference herein in its entirety. In some
embodiments, the electrolyte additive is at least one selected from
the group consisting of a solid electrolyte interphase (SEI)
improving agent, a cathode protection agent, a flame retardant
additive, LiPF.sub.6 salt stabilizer, an overcharge protector, an
aluminum corrosion inhibitor, a lithium deposition agent or
improver, or a solvation enhancer, an aluminum corrosion inhibitor,
a wetting agent, and a viscosity improver. In some embodiments the
additive can have more than one property, such as it can be a
wetting agent and a viscosity improver.
[0087] Exemplary SEI improving agents include VEC (vinyl ethylene
carbonate), VC (vinylene carbonate), FEC (fluoroethylene
carbonate), LiBOB (Lithium bis(oxalato) borate). Exemplary cathode
protection agents include N,N'-dicyclohexylcarbodiimide,
N,N-diethylamino trimethylsilane, LiBOB. Exemplary flame-retardant
additives include TTFP (tris(2,2,2-trifluoroethyl) phosphate),
fluorinated propylene carbonates, MFE (methyl nonafluorobuyl
ether). Exemplary LiPF.sub.6 salt stabilizers include LiF,TTFP
(tris(2,2,2-trifluoroethyl) phosphite), 1-methyl-2-pyrrolidinone,
fluorinated carbamate, hexamethyl-phosphoramide. Exemplary
overcharge protectors include xylene, cyclohexylbenzene, biphenyl,
2, 2-diphenylpropane, phenyl-tert-butyl carbonate. Exemplary Li
deposition improvers include AlI.sub.3, SnI.sub.2,
cetyltrimethylammonium chlorides, perfluoropolyethers,
tetraalkylammonium chlorides with a long alkyl chain. Exemplary
ionic salvation enhancer include 12-crown-4, TPFPB
(tris(pentafluorophenyl)). Exemplary A1 corrosion inhibitors
include LiBOB, LiODFB, such as borate salts. Exemplary wetting
agents and viscosity dilutersinclude cyclohexane and
P.sub.2O.sub.5. In some embodiments, the electrolyte additive is
air stable or resistant to oxidation. A battery separator
comprising the electrolyte additive disclosed herein can have a
shelf life of weeks to months, e.g. one week to 11 months.
[0088] In some embodiments, the additive can comprise, consist of,
or consist essentially of an energy dissipative non-miscible
additive. Non-miscible means that the additive is not miscible with
the polymer used to form the layer of the multilayer microporous
membrane or membrane that contains the additive.
[0089] In some embodiments, the membrane or membrane has or
exhibits increased or improved puncture strength compared to a
tri-layer microporous membrane or a three layer (trilayer)
multilayer microporous membrane. For example, the puncture strength
may be above 250 g, above 260 g, above 270 g, above 280 g, above
290 g, above 300 g, or above 310 g. In preferred embodiments the
puncture is greater than or equal to 300 g or greater than or equal
to 310 g. The multilayer membrane described herein may also have
improved MD shrinkage at 120.degree. C. for 1 hour compared to a
tri-layer microporous membrane or a three layer (trilayer)
multilayer microporous membrane. For example, MD shrinkage at
120.degree. C. for 1 hour may be less than 25%, less than 24%, less
than 23%, less than 22%, less than 21%, or less than 20%. In
preferred embodiments it is less than 24% or less than 20%. It can
be less than 15%. The multilayer membrane described herein may also
have improved MD tensile @ break. For example, the MD tensile at
break may be greater than 900 kg/cm.sup.2, or greater than 1,000
kg/cm.sup.2 or greater than 1,100 kg/cm.sup.2. These properties are
of the membrane itself, i.e., without a coating or other treatment.
In some embodiments, these properties may be exhibited in a TD
stretched product.
[0090] In some embodiments, at least one layer of the multilayer
membrane or membrane described herein comprises a polymeric
additive. The polymeric additive is added in an amount less than
the main polymer that the membrane is made up of. For example, in
some embodiments, the principle polymer can be a polyolefin. This
is another way of saying that at least one layer of the multilayer
membrane or membrane described herein comprises or is made up of a
polymeric blend. In some embodiments, the layer can comprise or be
made up of a polymeric or polymer blend and one or more of the
other additives described herein.
[0091] In some embodiments, the layer comprising the polymer blend
is an outer layer, such as a first outer layer or an opposite
second outer layer. In some instances, both a first outer layer and
a second outer layer comprise a polymer blend. In some embodiments,
an inner layer comprises a polymer blend. In some instances at
least one inner and at least one outer layer comprises a polymer
blend, and in some embodiments, all of the inner layers and all of
the outer layers comprise a polymer blend.
[0092] In some embodiments, the polymer blend comprises, consists
of, or consists essentially of at least two different polyolefins,
such as at least two different polyethylenes, at least two two
different polypropylenes, or a combination of at least one
polyethylene and one polypropylene. In some embodiments, the
polymer blend comprises, consists of, or consists essentially of a
polyolefin and a non-polyolefin, i.e., a polymer that is not a
polyolefin.
[0093] In some embodiments, each layer of the multilayer membrane
or membrane has a different compositions than the layers adjacent
to them. For example, one layer can comprise a polymer blend of two
different polyolefins, and one adjacent layer can comprise a
polymer blend of a polyolefin and a non-polyolefin, and the other
adjacent does not comprise a polymer blend.
[0094] The multilayer membrane can be stretched in a machine
direction (MD) to make the multilayer membrane microporous. In some
instances, the microporous multilayer membrane is produces by
transverse direction (TD) stretching of the MD stretched
microporous multilayer membrane. In addition to a sequential MD-TD
stretching, the multilayer membrane can also simultaneously undergo
a biaxial MD-TD stretching. Moreover, the simultaneous or
sequential MD-TD stretched microporous multilayer membrane can be
followed by a subsequent calendering step to reduce the membrane's
thickness, reduce roughness, reduce percent porosity, increase TD
tensile strength, increase uniformity, and/or reduce TD
splittiness. In some embodiments, the multilayer membrane is TD
stretched 1.times., 2.times., 3.times., 4.times., 5.times.,
6.times., 7.times., 8.times., 9.times., 10.times., or more than
10.times..
[0095] In an embodiment, a multilayer membrane can be manufactured
using an exemplary process that includes stretching and a
subsequent calendering step such as a machine direction stretching
followed by transverse direction stretching (with or without
machine direction relax) and a subsequent calendering step as a
method of reducing the thickness of such a stretched membrane, for
example, a multilayer porous membrane, in a controlled manner, to
reduce the percent porosity of such a stretched membrane, for
example, a multilayer porous membrane, in a controlled manner,
and/or to improve the strength, properties, and/or performance of
such a stretched membrane, for example, a multilayer porous
membrane, in a controlled manner, such as the puncture strength,
machine direction and/or transverse direction tensile strength,
uniformity, wettability, coatability, runnability, compression,
spring back, tortuosity, permeability, thickness, pin removal
force, mechanical strength, surface roughness, hot tip hole
propagation, and/or combinations thereof, of such a stretched
membrane, for example, a multilayer porous membrane, in a
controlled manner, and/or to produce a unique structure, pore
structure, material, membrane, base film, and/or separator.
[0096] In some instances, the TD tensile strength of the multilayer
membrane can be further improved by the addition of a calendering
step following TD stretching. The calendering process typically
involves heat and pressure that can reduce the thickness of a
porous membrane. The calendering process step can recover the loss
of MD and TD tensile strength caused by TD stretching. Furthermore,
the increase observed in MD and TD tensile strength with
calendering can create a more balanced ratio of MD and TD tensile
strength which can be beneficial to the overall mechanical
performance of the multilayer membrane.
[0097] The calendering process can use uniform or non-uniform heat,
pressure and/or speed to selectively densify a heat sensitive
material, to provide a uniform or non-uniform calender condition
(such as by use of a smooth roll, rough roll, patterned roll, micro
pattern roll, nano pattern roll, speed change, temperature change,
pressure change, humidity change, double roll step, multiple roll
step, or combinations thereof), to produce improved, desired or
unique structures, characteristics, and/or performance, to produce
or control the resultant structures, characteristics, and/or
performance, and/or the like. In an embodiment, a calendering
temperature of 50.degree. C. to 70.degree. C. and a line speed of
40 to 80 ft/min can be used, with a calendering pressure of 50 to
200 psi. The higher pressure can in some instances provide a
thinner separator, and the lower pressure provide a thicker
separator. These exemplary processing conditions are all
non-limiting.
[0098] In some embodiments, one or more coating layers can be
applied to one or two sides of the multilayer membrane. In some
embodiments, one or more of the coatings can be a ceramic coating
comprising, consisting of, or consisting essentially of a polymeric
binder and organic and/or inorganic particles. In some embodiments,
only a ceramic coating is applied to one or both sides of the
microporous membrane. In other embodiments, a different coating can
be applied to the microporous membrane before or after the
application of the ceramic coating. The different additional
coating can be applied to one or both sides of the membrane or film
also. In some embodiments, the different polymeric coating layer
can comprise, consist of, or consist essentially of at least one of
polyvinylidene difluoride (PVdF) or polycarbonate (PC).
[0099] In some embodiments, the thickness of the coating layer is
less than about 12 .mu.m, sometimes less than 10 .mu.m, sometimes
less than 9 .mu.m, sometimes less than 8 .mu.m, sometimes less than
7 .mu.m, and sometimes less than 5 .mu.m. In at least certain
selected embodiments, the coating layer is less than 4 .mu.m, less
than 2 .mu.m, or less than 1 .mu.m.
[0100] The coating method is not so limited, and the coating layer
described herein can be coated onto a porous substrate by at least
one of the following coating methods: extrusion coating, roll
coating, gravure coating, printing, knife coating, air-knife
coating, spray coating, dip coating, or curtain coating. The
coating process can be conducted at room temperature or at elevated
temperatures.
[0101] The coating layer can be any one of nonporous, nanoporous,
microporous, mesoporous or macroporous. The coating layer can have
a JIS Gurley of 700 or less, sometimes 600 or less, 500 or less,
400 or less, 300 or less, 200 or less, or 100 or less.
[0102] One or more layers, treatments, materials, or coatings (CT)
and/or nets, meshes, mats, wovens, or non-wovens (NW) can be added
on one or both sides, or within the multilayer film or membrane (M)
described herein, which can include but not limited to CT/M,
CT/M/CT, NW/M, NW/M/NW, CT/M/NW, CT/NW/M/NW/CT, CT/M/NW/CT,
etc.
II. Battery Separator
[0103] In some embodiments, a battery separator herein comprises,
consists of, or consists essentially of a (i.e., one or more)
multilayer membranes or multilayer microporous membranes, and
optionally a coating layer on one or both sides of the membrane.
The membrane itself, i.e., without a coating or any other
additional components, exhibits the improved properties described
above. The performance of the membranes can be further enhanced by
the addition of coatings or other additional components, such as
nonwovens, net, mesh, or the like on one or both sides, with or
without a coating, and/or by the described MD, MD-TD or MD-TD-C
stretching and calendering.
III. Composite Vehicle or Device
[0104] In an aspect, a composite comprises a multilayer membrane or
battery separator as described in Sections I and II, and one or
more electrodes, e.g., an anode, a cathode, or an anode and a
cathode, provided in direct contact therewith. The type of
electrodes are not so limited. For example, the electrodes can be
those suitable for use in a lithium ion secondary battery.
[0105] A suitable anode can have an energy capacity greater than or
equal to 372 mAh/g, preferably .gtoreq.700 mAh/g, and most
preferably .gtoreq.1000 mAH/g. The anode be constructed from a
lithium metal foil or a lithium alloy foil (e.g. lithium aluminum
alloys), or a mixture of a lithium metal and/or lithium alloy and
materials such as carbon (e.g. coke, graphite), nickel, copper. The
anode is not made solely from intercalation compounds containing
lithium or insertion compounds containing lithium.
[0106] A suitable cathode can be any cathode compatible with the
anode and can include an intercalation compound, an insertion
compound, or an electrochemically active polymer. Suitable
intercalation materials includes, for example, MoS.sub.2,
FeS.sub.2, MnO.sub.2, TiS.sub.2, NbSe.sub.3, LiCoO.sub.2,
LiNiO.sub.2, LiMn.sub.2O.sub.4, V.sub.6O.sub.13, V.sub.2O.sub.5,
and CuCl.sub.2. Suitable polymers include, for example,
polyacetylene, polypyrrole, polyaniline, and polythiopene.
[0107] Any separator described hereinabove can be incorporated to
any vehicle or device, e.g., an e-vehicle, or device, e.g., a cell
phone or laptop, that is completely or partially battery
powered.
IV. Textile
[0108] In some embodiments, a textile comprising, consisting of, or
consisting essentially of the multilayer microporous membrane or
film described herein is described. In some preferred embodiments,
the textile comprises the multilayer microporous membrane or film
described herein and a non-woven or woven material. The non-woven
can be a staple non-woven, a melt-blown non-woven, a spunlaid
non-woven, a flashspun non-woven, an air-laid non-woven, or a
non-woven made by any other process. In some preferred embodiments,
the non-woven or woven is attached to the multilayer microporous
membrane or film. In some embodiments, a textile comprises,
consists of, or consists essentially of a woven or non-woven,
multilayer microporous membrane or film as described herein, and
another woven or non-woven in that order. In some embodiments, the
textile comprises, consists of, or consists essentially a
multilayer microporous membrane or film as described herein, a
non-woven or woven, and multilayer microporous membrane or film as
described herein, in that order.
V. Method of Making Multilayer Membranes
[0109] In some embodiments, the physical properties of the
multilayer membranes described herein are a result of, at least in
part, the method by which multilayer membranes are made.
[0110] In an aspect, a method comprises at least coextruding two or
more polymer mixtures to form a first coextruded bi-layer,
tri-layer, or multi-layer membrane, coextruding two or more other
polymer mixtures to form a second coextruded bi-layer, tri-layer,
or multi-layer membrane, and coextruding two or more further
polymer mixtures to form a third coextruded bi-layer, tri-layer, or
multi-layer membrane. The polymer mixtures used to form each layer
of the first, second, and third bi-layer, tri-layer, or multi-layer
layer membrane can be the same or different. The mixtures can only
include one polymer, or more than one polymer, such as polymer
blends. Also, more than three bi-layer, tri-layer, or multi-layer
membranes can be formed. After the first, second, and third
bi-layer, tri-layer, or multi-layer membrane is formed, the
membranes are laminated together with two of the membranes formed
on opposite surfaces of one of the membranes to form the
microporous battery separators described herein. The laminated
multilayer membrane can be uniaxially or biaxially stretched, and
in some instances calendered.
[0111] Each layer of the multi-layer membrane can comprise one or
more sublayers, microlayers, or plies formed by extrusion or
co-extrusion. Co-extrusion typically involves use of a co-extrusion
die with one or more extruders feeding the die (typically one
extruder per layer of the bi-layer, tri-layer, or multi-layer
membrane). An exemplary co-extrusion process is shown in FIG. 4 and
a co-extrusion die is shown in FIG. 5.
[0112] In some embodiments, the co-extrusion step is performed
using a co-extrusion die with one or more extruders feeding the
die. Typically, there is one extruder for each desired layer or
microlayer of the ultimately formed co-extruded film. For example,
if the desired co-extruded film has three microlayers, three
extruders are used with the co-extrusion die. In at least one
embodiment the multilayer membrane can be constructed of many
sublayers, microlayers, or nanolayers wherein the final product can
contain 2, 3, 4, 5, 6, 7, 8, 9, 10, or more layers of individual
sublayers, microlayers or nanolayers that together comprise a layer
in the multilayer membrane. In at least certain embodiments the
sublayer technology can be created by a pre-encapsulation feedblock
prior to entering a cast film or blown film die.
[0113] In some embodiments, the co-extrusion is an air bubble
co-extrusion method and the blow-up ration can be varied between
0.5 to 2.0, 0.7 to 1.8, or 0.9 to 1.5. Following co-extrusion using
this blow-up ratio, the film can be MD stretched, MD stretched and
then TD stretched (with or without MD relax) or simultaneously MD
and TD stretched, as described in more detail below. The film can
then be optionally calendered to further control porosity.
[0114] Co-extrusion benefits include but are not limited to
increasing the number of layers (interfaces), which without wanting
to be bound by any particular theory, is believed to improve
puncture strength. Also, co-extrusion, without wishing to be bound
by any particular theory, is believed to result in the observed DB
improvement. Specifically, DB improvement can be related to the
reduced PP pore size observed when a co-extrusion process is used.
Also, co-extrusion allows for a wider number of choices of
materials by incorporating blends in the microlayers. Co-extrusion
also allows formation of thin tri-layer or multi-layer films
(coextruded films). For example, a tri-layer co-extruded film
having a thickness of 8 or 10 microns or thinner can be formed.
Co-extrusion allows for higher MD elongation, different pore
structure (smaller PP, larger PE). Co-extrusion can be combined
with lamination to create desired inventive multi-layer structures.
For, example, structures as formed in the Examples.
[0115] The laminating step comprises bringing a surface of the
co-extruded film together with a surface of the at least one other
film and fixing the two surfaces together using heat, pressure, and
or heat and pressure. Heat can be used, for example, to increase
the tack of a surface of either or both of the co-extruded film and
the at least one other film to make lamination easier, making the
two surfaces stick or adhere together better. The number of
lamination steps are not so limited. For example, all of the layers
of the membrane may be laminated together or two layers may be
laminated together at a time. For example, two layers may be
laminated to form a laminate and then another layer may be
laminated to that laminate to form a second laminate, and then
another layer may be laminated to that second laminate to form a
third laminate, etc.
[0116] In some embodiments, the laminate formed by laminating the
co-extruded film to at least one other film is a precursor for
subsequent MD and/or TD stretching steps, with or without relax. In
some embodiments, the co-extruded films are stretched before
lamination.
[0117] Additional steps can comprise, consist of, or consist
essentially of an MD, TD, or sequential or simultaneous MD and TD
stretching steps. The stretching steps can occur before or after
the lamination step. Stretching can be performed with or without MD
and/or TD relax. Co-pending, commonly owned, U.S. Published Patent
Application Publication No. US2017/0084898 A1 published Mar. 23,
2017 is hereby fully incorporated by reference herein.
[0118] Other additional steps can include calendering. For example,
in some embodiments the calendering step can be performed as a
means to reduce the thickness, as a means to reduce the pore size
and/or porosity, and/or to further improve the transverse direction
(TD) tensile strength and/or puncture strength of the porous
biaxially stretched membrane precursor. Calendering can also
improve strength, wettability, and/or uniformity and reduce surface
layer defects that have become incorporated during the
manufacturing process e.g., during the MD and TD stretching
processes. The calendered film or membrane can have improved coat
ability (using a smooth calender roll or rolls). Additionally,
using a texturized calendering roll can aid in improved coating
adhesion to the film or membrane.
[0119] Calendering can be cold (below room temperature), ambient
(room temperature), or hot (e.g., 90.degree. C.) and can include
the application of pressure or the application of heat and pressure
to reduce the thickness of a membrane or film in a controlled
manner. Calendering can be in one or more steps, for example, low
pressure calendering followed by higher pressure calendering, cold
calendering followed by hot calendering, and/or the like. In
addition, the calendering process can use at least one of heat,
pressure and speed to densify a heat sensitive material. In
addition, the calendering process can use uniform or non-uniform
heat, pressure, and/or speed to selectively densify a heat
sensitive material, to provide a uniform or non-uniform calender
condition (such as by use of a smooth roll, rough roll, patterned
roll, micro-pattern roll, nano-pattern roll, speed change,
temperature change, pressure change, humidity change, double roll
step, multiple roll step, or combinations thereof), to produce
improved, desired or unique structures, characteristics, and/or
performance, to produce or control the resultant structures,
characteristics, and/or performance, and/or the like.
[0120] Another exemplary method of making a multilayer microporous
membrane comprises the steps of coextruding a nonporous
polypropylene precursor comprising a plurality of sublayers;
coextruding a nonporous polyethylene precursor comprising a
plurality of sublayers; laminating a plurality of the coextruded
polypropylene precursor layers with the extruded polyethylene
precursor layers to form a first intermediate precursor having
alternating polyethylene and polypropylene layers; simultaneously
laminating a first outer layer comprising the coextruded
polypropylene precursor to a first surface of the intermediate
precursor and a second outer layer comprising the coextruded
polypropylene precursor to a second surface of the first
intermediate precursor opposite the first surface to form a second
intermediate precursor; annealing the second intermediate precursor
to form an annealed multilayer membrane; stretching the annealed
multilayer membrane to form a microporous multilayer membrane,
wherein the stretching is uniaxial or biaxial; and optionally
calendering the microporous multilayer membrane. In some preferred
embodiments, calendering is performed. This method is non-limiting.
For example, the first intermediate precursor may comprise all
polyethylene or all polypropylene precursors.
[0121] In some instances, the first intermediate precursor
comprises a trilayer membrane having a structure of PE/PP/PE or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP), and the second intermediate
precursor comprises a penta-layer membrane having a structure of
PP/PE/PP/PE/PP or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP).
[0122] Each of the coextruded polypropylene precursor layers can
comprise a single monolayer or two, three, four, or more sublayers,
and each of the extruded polyethylene precursor can comprise a
single monolayer or two, three, four, or more sublayers. In one
embodiment, the second intermediate precursor comprises a
penta-layer membrane having a structure of PP/PE/PP/PE/PP, where
each layer comprises three sublayers. For example, the structure is
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP).
[0123] The coextruded polypropylene precursor and the polyethylene
precursor are nonporous, and can be made to be microporous through
the stretching steps. The uniaxial stretching can be in the machine
direction or the transverse direction, and the biaxial stretching
can be in the machine direction and transverse direction. The
biaxial machine direction and transverse direction stretching can
be sequential or simultaneous.
[0124] In some embodiments, there is a calendering step.
Calendering may comprise application of heat, pressure, or heat and
pressure.
[0125] In some embodiments, the method further comprising the step
of coating one or more of the first outer layer and the second
outer layer, such as in example where the membrane is a battery
separator.
[0126] In another embodiment of a method for making a pentalayer
membrane with a general structure of PP/PE/PP/PE/PP or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) and in some
embodiments a specific structure of
(PP1,PP2,PP3)/(PE1,PE2,PE3)/(PP1,PP2,PP3)/(PE1,PE2,PE3)/(PP1,PP2,PP3),
where each layer comprises three sublayers or plies, the method
comprises a Step 1 and a Step 2, as shown in FIG. 1.
[0127] FIG. 1 shows an exemplary method of making a pentalayered
membrane having a general structure of PP/PE/PP/PE/PP or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP). The
trilayer component may have a structure PE/PP/PE or
(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE). This is a two step process, but
the pentalayer may be formed in one step where all five layers are
laminated together. A method using more than two steps is also
possible.
[0128] In Step 1, an inverted trilayer membrane is created by
laminating a first layer of polyethylene to a first side of a
middle polypropylene layer, and laminating a second layer of a
polyethylene to a second side of the middle polypropylene layer to
give a trilayer having a structure of PE/PP/PE. A non-inverted
trilayer PP/PE/PP may also be formed. The first and second
polyethylene layers and the middle polypropylene layer of the
trilayer can each be a single monolayer, or have multiple
sublayers, as described above in Section I. In preferred
embodiments, each layer may comprise sublayers. In Step 2, the
trilayer is used as a middle layer, and a first outer polypropylene
layer (or polyethylene) is laminated to the first layer of
polyethylene or one side of the trilayer, and a second outer
polypropylene layer (or polyethylene) is laminated to the second
layer of polyethylene or an opposite side of the trilayer to give a
pentalayer membrane having a structure of PP/PE/PP/PE/PP. Again,
the first and second outer layers of polypropylene (or
polyethylene) can each be a single monolayer, or have multiple
sublayers, as described above in Section I. If the first and second
outer layers have multiple sublayers (2 or more), the thickness of
the outermost and exposed sublayer may be thicker than or thinner
than or the same thickness as the inner sublayers. In one
embodiment, each of the layers in the pentalayer membrane comprise
3 sublayers, for a total of 15 sublayers. Structure is
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP).
[0129] In yet another exemplary method of making a pentalayered
microporous membrane, the method comprises the steps of extruding a
plurality of polypropylene membranes and polyethylene membranes;
laminating one of the polyethylene membranes to a first side of a
polypropylene membrane and another one of the polyethylene
membranes to an opposite second side of the polypropylene membrane
to form an inverted trilayer membrane having a structure of
PE/PP/PE or (PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE); laminating one of the
polypropylene layers to one of the polyethylene membranes in the
trilayer membrane and another of the polypropylene layers to the
other polyethylene membrane in the trilayer membrane to form a
penta-layer membrane having a structure of PP/PE/PP/PE/PP or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP); stretching
the annealed multilayer membrane to form a microporous multilayer
membrane, wherein the stretching is uniaxial or biaxial; and
optionally calendering the microporous multilayer membrane. In some
embodiments, the trilayer can be PP/PE/PP or
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) and the pentalayer structure may
be (PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE). The
trilayer may also be all PP or all PE, e.g., PP/PP/PP or PE/PE/PE
or (PP/PP/PP)/(PP/PP/PP)/(PP/PP/PP) or
(PE/PE/PE)/(PE/PE/PE)/(PE/PE/PE). The pentalayer may be
PE/PP/PP/PP/PE or PP/PE/PE/PE/PP or
(PE/PE/PE)/(PP/PP/PP)/(PP/PP/PP)/(PP/PP/PP)/(PE/PE/PE) or
(PP/PP/PP)/(PE/PE/PE)/(PE/PE/PE)/(PE/PE/PE)/(PP/PP/PP).
Example 1
Composition of Experimental Penta-Layer
[0130] The composition of the Experimental penta-layer membrane is
(PP1/PP1/PP1)/(PE1/PE1/PE1)/(PP1/PP1/PP1)/(PE1/PE1/PE1)/(PP1/PP1/PP1),
where PP1 is homopolymer PP, density range of 0.90-0.92 g/cm.sup.3,
MFR in the range of 0.5MFR-2MFR. A11 PE1 layers are high density
polyethylene with melt index between 0.25-0.5 g/10 min at 2.16 kg
and 190 deg C, and density range between 0.95-0.97 g/cm.sup.3.
Method of Making the Penta-Layer:
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)
[0131] The penta-layer membrane of EXAMPLE 9 having a structure of
(PP1/PP1/PP2)/(PE2/PE2/PE2)/(PP1/PP2/PP1)/(PE2/PE2/PE2)/(PP2/PP1/PP1)
was manufactured by coextruding layers having a structure
(PP1/PP1/PP2), layers having a structure (PE2/PE2/PE2), layers
having a structure (PP1/PP2/PP1) and layers having a structure
(PP2/PP1/PP1). These co-extruded layers were then laminated
together to form an intermediate having a structure of
(PP1/PP1/PP2)/(PE2/PE2/PE2)/(PP1/PP2/PP1)/(PE2/PE2/PE2)/(PP2/PP1/PP1)
and the intermediate was stretched in the MD and TD directions and
then calendered.
[0132] The penta-layer is shown schematically in FIGS. 6 and 3b.
The PP1:PP2:PP1 ratio is 1:1:1. The PP1:PP1:PP2 ratio is 1:1:1. The
PP:PE:PP:PE:PP ratio is 15:10:15:10:15. Total PE amount is 30%.
SEM Images of MD, TD, and TDC
[0133] FIG. 7 show a scanning electron microscope (SEM) image of a
penta-layered membrane having a general structure of
PP/PE/PP/PE/PP, where each layer (e.g., PP of the structure
PP/PE/PP/PE/PP is considered a layer) has three sublayers (for a
combined total of 15 sublayers). See, for example, FIG. 3b and FIG.
6. The SEM micrograph in FIG. 7 marked "MD" is of the penta-layered
membrane after being stretched uniaxially in the MD. The pores have
a rectangular slit-shape. The SEM micrograph in FIG. 7 marked "TD"
is of the penta-layered membrane after a sequential MD-TD
stretching. As shown in the SEM micrograph in FIG. 7 marked "TD",
there is a more open porous structure of the inner PE microporous
layers sandwiched by PP microporous layers, and the pores have an
approximate round-shape appearance. The SEM micrograph marked "TDC"
in FIG. 7 is of the penta-layered membrane after a combined TD
stretching and subsequent calendering (TDC) of the MD-stretched
membrane in the SEM micrograph of FIG. 7 marked "MD." The
calendering process involves heat and pressure and can reduce the
thickness of the membrane in a controlled fashion.
EXAMPLE 2 (Tri-Layer 1)
Composition of the First Tri-layer (tri-layer 1): PP1/PE1/PP1
[0134] All PP1 layers are made of a homopolymer PP density range of
0.90-0.92 g/cm{circumflex over ( )}3, MFR in the range of
0.5MFR-2MFR. All PE1 layers are high density polyethylene with melt
index between 0.25-0.5 g/10 min at 2.16 kg and 190 deg C, and
density range between 0.95-0.97 g/cm.sup.3.
Method of Making Tri-Layer 1: PP1/PE1/PP1
[0135] The first trilayer of Example 5 was formed by extruding two
PP monolayers and a PE monolayer. Next, the monolayers were
laminated so that the two PP monolayers were laminated on either
side of the PE monolayer to form an intermediate, which was then
stretched in the MD and TD and then calendered. The monolayers may
be laminated all together or one PP monolayer may be laminated to
the PE monolayer and then the other PP monolayer may be laminated.
The PP:PE:PP ratio is 2:1:2, with the total amount of PE being
20%.
[0136] The first trilayer is shown schematically in FIG. 4 and FIG.
3c.
Example 3 (Tri-Layer 2)
Composition of the Tri-Layer 2
[0137] The composition of the second tri-layer is
(PP1/PP2/PP1)/(PE2/PE2/PE2)/(PP1/PP2/PP1) PP1 is homopolymer PP,
density range of 0.90-0.92 g/cm.sup.3, MFR in the range of
0.5MFR--2MFR. PP2 is blend made of 90% of the homopolymer PP in PP1
and 10% of a propylene-ethylene elastomer. PE1 is made of a blend
of 95% high density polyethylene with a melt index between 0.25-0.5
g/10 min at 2.16 Kg and 190 degrees centigrade and a density range
between 0.95-0.97 g/cm.sup.3 and 5% mLLDPE.
Method of Making the Tri-Layer 2
[0138] Tri-layer 2 was formed by co-extruding PP-containing layers
having the composition described in Example 7 above (i.e.,
PP1/PP2/PP1) and PE-containing layers having the composition
described in Example 7 above (i.e., PE2/PE2/PE2), each of the
PP-containing layers and the PE-containing layers having three
sub-layers as shown in FIG. 3a. Then, two PP-containing layers were
laminated on either side of a PE-containing layer to form an
intermediate. This intermediate was then MD and TD stretched and
then calendered.
[0139] Tri-layer 2 is shown schematically in FIGS. 5 and 3a. The
PP1:PP2:PP1 ratio is 1:1:1. The PP:PE:PP ratio is 2:1:2. Total PE
is 20%.
Example 4 (Second Pentalayer)
Composition of Second Pentalayer
[0140] Second pentalayer has a structure PP1/PE1/PP1/PE1/PP1, where
PP1 and PE1 are as described herein.
Method of Making Second Pentalayer
[0141] Second pentalayer is formed by extruding monolayers made of
PP1 and PE1 respectively, and then laminating those monolayers to
form a structure PP1/PE1/PP1/PE1/PP1. This laminate was the MD and
TD stretched and then calendered.
Example 5 (Collapsed Bubble Co-Extrusion)
Composition
[0142] The composition of Example 5 has a structure
PP1/PP2/PE1/PE1/PP2/PP1, where PP1, PP2, and PE1 are as described
herein.
Method of Making
[0143] Example 5 was formed by co-extruding a trilayer PP1/PP2/PE1
using a bubble extrusion method and collapsing the bubble which
results in lamination of the PE1 layers on either side of the
bubble to one another. This laminate was then the MD and TD
stretched and then calendered. This embodiment has one lamination
interface and it is a PE/PE lamination interfaces.
Example 6 (Multilaminate)
Composition of Example 5
[0144] Example 6 has a structure PP1/PP2/PE1/PE1/PP2/PP1 where PP1,
PP2, and PE1 are as described herein.
Method of Making Example 6
[0145] Six monolayers were co-extruded (2 PP1 monolayers, 2PP2
monolayers, and 2 PE1 monolayers), and they were laminated together
to form the structure of Example 6, which has 5 lamination
interfaces (only 2 PP/PE lamination interfaces). This laminate was
then the MD and TD stretched and then calendered.
Example 7 (Multilaminate)
Composition
[0146] Example 7 has a structure PP1/PE1/PP2/PP2/PE1/PP1 where PP,
PP2, and PE 1 are as described herein.
Method of Making Example 7
[0147] Six monolayers (2 PP1 monolayers, 2 PE1 monolayers, and 2
PP2 monolayers) were extruded and laminated together to form the
structure above. This laminate was then the MD and TD stretched and
then calendered. This laminate has 5 lamination interfaces. It has
4 PP/PE lamination interfaces.
Results
Comparison of MD-stretched Penta-layered Membrane of Example 1
[0148] Table 1 below shows the comparative properties of a uniaxial
MD-stretched penta-layered membrane 1 (Example 1) having a
composition and structure
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) shown in
FIG. 3b in comparison with an MD-stretched first tri-layer membrane
(Example 2) having the composition and structure (PP/PE/PP) shown
in FIG. 3c and second tri-layer membrane (Example 3) having a
composition and structure (PP/PE/PP) shown in FIG. 3a. As shown
below, each of the layers in FIG. 3b comprise three sublayers each,
and the layers of the second tri-layer in FIG. 3a also comprises
sublayers. Notably, FIGS. 3a-3c are not drawn to scale, but,
rather, are drawn to show the where the first and second trilayers
correspond to portions of the penta-layered membrane. As shown in
Tables 1-3, the overall thickness of the first and second trilayers
is approximately equal (with some variations disclosed in the Table
1-3) to the overall thickness of the penta-layer membrane. Thus,
each sublayer in the penta-layer membrane has a smaller average
thickness than the average thickness of the corresponding sublayer
in the first and second trilayers. The PP material and PE material
used in the pentalayered membrane and the second trilayer membrane
are identical.
TABLE-US-00001 TABLE 1 Comparative properties of an MD-stretched
Penta-layered Membrane of Example 1 compared to MD stretched First
and Second Tri-layer of Comparative Examples 1 and 2. First Second
Penta- Property Units Tri-layer Tri-layer layer Thickness Microns
42 39 37 Gurley S 2,400 7,500 2,300 Relative Gurley 1.0 3.1 1.0
Puncture g 850 780 1000 MD shrinkage @ % 4.9 9.5 12.0 120.degree.
C. for 1 hr MD tensile @ kg/cm.sup.2 2,050 1,950 2,600 break TD
tensile @ kg/cm.sup.2 140 160 155 break TD elongation @ % 620 1,020
1,080 break
TD-Stretched Comparison of Penta-Layered Membrane of Example 1 with
the First and Second Tri-Layers of Examples 2 and 3
[0149] Table 2 below shows the comparative properties of a TD
stretched penta-layered membrane having a composition and structure
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) shown in
FIG. 3b in comparison with an TD-stretched first tri-layer membrane
having the composition and structure (PP/PE/PP) shown in FIG. 3c
and second tri-layer membrane having a composition and structure
(PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) shown in FIG. 3a.
TABLE-US-00002 TABLE 2 Comparative properties of a TD-stretched
Penta-layered Membrane First Tri-layer Second tri-layer Penta-layer
Property Units (Example 2) (Example 3) (Example 1) Stretch ratio %
450 600 450 600 450 600 Gurley s 101 60 80 -- 85 80 Thickness
microns 28 23 20 -- 20 16 Puncture g 290 220 280 -- 310 255 MD
shrinkage @ % 21.2 41.0 23.0 -- 16.7 23.4 120.degree. C. for 1 hr
TD shrinkage@ % 4.0 9.0 9.3 -- 12.5 14.4 120.degree. C. for 1 hr MD
Tensile @ break kg/cm.sup.2 880 605 916 -- 1,160 1,185 MD
elongation@ break % 112 78 145 -- 93 92 MD Modulus kg/cm.sup.2
2,598 2,604 TD tensile @ break kg/cm.sup.2 380 420 494 -- 355 455
TD elongation @ break % 158 89 115 -- 97 76 TD modulus kg/cm.sup.2
1,743 1,995 Calculated porosity % 68 75 67 -- 64 65 Dielectric
Breakdown V 1,620 -- -- 1,750
Comparison of TDC Penta-Layered Membrane of Example 1 with the
First and Second Tri-Layers of Examples 2 and 3
[0150] Table 3 below shows the comparative properties of a
TD-stretched and calendered penta-layered membrane having a
composition and structure
(PP/PP/PP)/(PE/PE/PE)/(PP/PP//PP)/(PE/PE/PE)/(PP/PP/PP) shown in
FIG. 3b in comparison with TD stretched and calendered tri-layer
membrane having the composition and structure (PP/PE/PP) shown in
FIG. 3c and second tri-layer membrane having a composition and
structure (PP/PP/PP)/(PE/PE/PE)/(PP/PP/PP) shown in FIG. 3a.
TABLE-US-00003 TABLE 3 Comparative properties of a TD-stretched and
calendered Penta-layered Membrane First Second Penta- tri-layer
Tri-layer layer Property Units (Example 2) (Example 3) (Example 1)
Gurley s 130 200 200 Thickness Microns 14 14 14 Puncture g 340 360
380 MD shrinkage@ % 26.0 15.2 15.3 120.degree. C. for 1 hour TD
shrinkage @ % 10.0 5.9 14.1 120.degree. C. for 1 hour MD tensile @
kg/cm.sup.2 1,300 1,350 1,780 break TD tensile @ kg/cm.sup.2 775
625 510 break Dielectric V 1,657 1,916 -- Breakdown DB standard V
79 57 deviation DB minimum V 1,460 1,800 Porosity, % 52 44
intrusion Porosity, % 41 Calculated
As can be seen by the comparison of the penta-layered embodiment
(Example 1) with the two tri-layer embodiments (Example 2 and
Example 3), the penta-layered embodiment exhibits, for example,
improved puncture. This is believed to be due at least in part to
the lamination interfaces compared to the first trilayer, which has
none and/or the increased number of lamination interfaced compared
to the second-trilayer, which has two lamination interfaces. It is
hypothesized that three or more lamination interfaces improves
properties of the microporous membrane. It has been shown that four
lamination interfaces improve the property of the microporous
film.
[0151] Table 4 compares properties of MD-stretched Trilayer 1
(Example 2) and second pentalayer (Example 4)
TABLE-US-00004 Second Trilayer 1 Pentalayer Property Units (Example
2) (Example 4) Relative JIS -- 1.0 1.0 Gurley Puncture g/micron
17.2 21.4 MD Tensile @ Kg/cm.sup.2 1,700 2,150 Break TD Elongation
@ % 950 1,020 break
[0152] Table 5 compares properties of MD and TD-stretched Trilayer
1 (Example 2) and second pentalayer (Example 4)
TABLE-US-00005 Second Trilayer 1 Pentalayer Property Units (Example
2) (Example 4) Relative JIS -- 1.0 0.7 Gurley Puncture g/micron
10.0 8.8 MD Tensile @ Kg/cm.sup.2 750 1,000 Break
[0153] Table 6 compares properties of MD and TD stretched and then
calendered Trilayer 1 (Example 2) and second pentalayer (Example
4)
TABLE-US-00006 Second Trilayer 1 Pentalayer Property Units (Example
2) (Example 4) Relative JIS -- 1.0 1.0 Gurley Puncture g/micron
17.9 23.3 MD tensile @ Kg/cm.sup.2 1,200 1,700 break
Thus, Tables 4-6 show improvement in a product having 4 lamination
interfaces (second pentalayer, Example 4) compared to a product
having 2 lamination interfaces (trilayer 1, Example 2). In these
Examples, each of the lamination interfaces are PP/PE lamination
interfaces where the layers or sublayers at the interfaces are PP
on one side of the interface and PE on the other.
[0154] Normalized puncture strength for Examples 1 to 7 is shown in
FIG. 8. In FIG. 8, the "a" value is a normalized puncture strength
value calculated as shown in the figure. From the results in FIG.
8, some conclusions are that the number of PP/PE interfaces had a
strong influence on resulting strength of the Example. Compare
Example 2 with 2 PP/PE lamination interfaces to Example 4 with 4
PP/PE lamination interfaces. Compare Example 4 with 4 lamination
interfaces to Example 7 with 5 lamination interfaces. Compare
Example 2 with Example 6. These have 2 and 5 lamination interfaces,
respectively, but the same number of PP/PE lamination
interfaces.
[0155] In at least another embodiment, the porous membrane could be
a base film for coating, dipping or impregnation, for example, a
base film for a gradient or controlled impregnation or coating (for
example, if a partially pre-wetted membrane was coated with a PO
dipping solution). The coating would in this case only partially
impregnate the membrane. There could be a controlled impregnation,
for example, where the dipping material is a blend of two polymer
resins where one more easily penetrates the membrane than the other
(which would remain near the surface).
[0156] The membrane or separator may be a cut piece, slit, leaf,
sleeve, pocket, envelope, wrap, Z fold, serpentine, and/or the
like. The membrane or separator may be a flat sheet, tape, slit,
non-woven, woven, mesh, knit, hollow fiber, and/or the like. The
membrane or separator may be adapted for use in a electrochemical
device, battery, cell, ESS, UPS, capacitor, supercapcitor, double
layer capacitor, fuel cell (PEM, humidity control membrane,..),
catalyst carrier, carrier, pancake (anode, separator, cathode),
base film, coated base film, textile, barrier layer in textile,
hazmat suit, barrier layer in hazmat suit, blood barrier, water
barrier, filtration media, blood, blood components, blood
oxygenator, disposable lighter, and/or the like.
[0157] The instant battery separator may be a co-extruded,
multi-layered battery separator. Co-extruded refers to a process
where polymers are simultaneously brought together in an extrusion
die and exit from the die in a form, here a generally planar
structure, having at least two discrete layers joined together at
the interface of the discrete layers by, for example, a commingling
of the polymers forming the interface of the discrete layers. The
extrusion die may be either a flat sheet (or slot) die or a blown
film (or annular) die. The co-extrusion process shall be described
in greater detail below. Multi-layered refers to a separator having
at least two layers. Multi-layered may also refer to structures
with 3, 4, 5, 6, 7, or more layers. Each layer is formed by a
separate polymer feed stream into the extrusion die. The layers may
be of differing thicknesses. Most often, at least two of the feed
streams are of dissimilar polymers. Dissimilar polymer refers to:
polymers having dissimilar chemical natures (e.g., PE and PP, or PE
and a co-polymer of PE are polymers having dissimilar chemical
natures); and/or polymer having the same chemical nature but
dissimilar properties (e.g., two PE's having differing properties
(e.g., density, molecular weights, molecular weight distributions,
rheology, additives (composition and/or percentage), etc.))
However, the polymers may be the same or identical.
[0158] The polymers that may be used in the instant battery
separator are those that are extrudable. Such polymers are
typically referred to as thermoplastic polymers. Exemplary
thermoplastic polymers include, but are not limited to:
polyolefins, polyacetals (or polyoxymethylenes), polyamides,
polyesters, polysulfides, polyvinyl alcohols, polyvinyl esters, and
polyvinylidenes. Polyolefins include, but are not limited to:
polyethylene (including, for example, LDPE, LLDPE, HDPE, UHDPE),
polypropylene, polybutylene, polymethylpentane, co-polymers
thereof, and blends thereof. Polyamides (nylons) include, but are
not limited to: polyamide 6, polyamide 66, Nylon 10,10,
polyphthalamide (PPA), co-polymers thereof, and blends thereof.
Polyesters include, but are not limited to: polyester
terephalthalate, polybutyl terephalthalate, co-polymers thereof,
and blends thereof. Polysulfides include, but are not limited to,
polyphenyl sulfide, co-polymers thereof, and blends thereof.
Polyvinyl alcohols include, but are not limited to: ethylene-vinyl
alcohol, co-polymers thereof, and blends thereof. Polyvinyl esters
include, but are not limited to, polyvinyl acetate, ethylene vinyl
acetate, co-polymers thereof, and blends thereof. Polyvinylidenes
include, but are not limited to: fluorinated polyvinylidenes (e.g.,
polyvinylidene chloride, polyvinylidene fluoride), co-polymers
thereof, and blends thereof.
[0159] Various materials may be added to the polymers. These
materials are added to modify or enhance the performance or
properties of an individual layer or the overall separator.
[0160] Materials to lower the melting temperature of the polymer
may be added. Typically, the multi-layered separator includes a
layer designed to close its pores at a predetermined temperature to
block the flow of ions between the electrodes of the battery. This
function is commonly referred to as `shutdown.` In one embodiment,
a trilayer separator has a middle shutdown layer. To lower the
shutdown temperature of the layer, materials, with a melting
temperature less than the polymer to which they are mixed, may be
added to the polymer. Such materials include, but are not limited
to: materials with a melting temperature less than 125.degree. C.,
for example, polyolefins or polyolefin oligomers. Such materials
include, but are not limited to: polyolefin waxes (polyethylene
wax, polypropylene wax, polybutene wax, and blends thereof). These
materials may be loaded into the polymer at a rate of 5-50 wt % of
the polymer. Shutdown temperatures below 140 degree C. are
obtainable in one embodiment. Shutdown temperatures below 130
degree C. are obtainable in other embodiments.
[0161] Materials to improve the melt integrity of the membrane may
be added. Melt integrity refers to the ability of the membrane to
limit its loss or deterioration of its physical dimension at
elevated temperatures such that the electrodes remain physically
separated. Such materials include mineral fillers. Mineral fillers
include, but are not limited to: talc, kaolin, synthetic silica,
diatomaceous earth, mica, nanoclay, boron nitride, silicon dioxide,
titanium dioxide, barium sulfate, calcium carbonate, aluminum
hydroxide, magnesium hydroxide and the like, and blends thereof.
Such materials may also include, but are not limited to, fine
fibers. Fine fibers include glass fibers and chopped polymer
fibers. Loading rates range from 1-60 wt % of the polymer of the
layer. Such materials may also include high melting point or high
viscosity organic materials, e.g., PTFE and UHMWPE. Such materials
may also include cross-linking or coupling agents.
[0162] Materials to improve the strength or toughness of the
membrane may be added. Such materials include elastomers.
Elastomers include, but are not limited to: ethylene-propylene
(EPR), ethylene-propylene-diene (EPDM), styrene-butadiene (SBR),
styrene isoprene (SIR), ethylidene norbornene (ENB), epoxy, and
polyurethane and blends thereof. Such materials may also include,
but are not limited to, fine fibers. Fine fibers include glass
fibers and chopped polymer fibers. Loading rates range from 2-30 wt
% of the polymer of the layer. Such materials may also include
cross-linking or coupling agents or high viscosity or high melting
point materials.
[0163] Materials to improve the antistatic properties of the
membrane may be added. Such materials include, for example,
antistatic agents. Antistatic agents include, but are not limited
to, glycerol monostreates, ethoxylated amines, polyethers (e.g.,
Pelestat 300, commercially available from Sanyo Chemical Industrial
of Japan). Loading rates range from 0.001-10 wt % of the polymer of
the layer.
[0164] Materials to improve the surface wettability of the
separator may be added. Such materials include, for example,
wetting agents. Wetting agents include, but are not limited to,
ethoxylated alcohols, primary polymeric carboxylic acids, glycols
(e.g., polypropylene glycol and polyethylene glycols), polyolefin
functionalized with maleic anhydride, acrylic acid, glycidyl
methacrylate. Loading rates range from 0.01-10 wt % of the polymer
of the layer.
[0165] Materials to improve the surface tribology performance of
the separator may be added. Such materials include lubricants.
Lubricants include, for example, fluoropolymers (e.g.,
polyvinylidene fluoride, polytetrafluoroethylene, low molecular
weight fluoropolymers), slip agents (e.g., oleamide, stearamide,
erucamide, Kemamide.RTM., calcium stearate, silicone. Loading rates
range from 0.001-10 wt % of the polymer of the layer.
[0166] Materials to improve the polymer processing may be added.
Such materials include, for example, fluoropolymers, boron nitride,
polyolefin waxes. Loading rates range from 100 ppm to 10 wt % of
the polymer of the layer.
[0167] Materials to improve the flame retardant nature of the
membrane may be added. Such materials include, for example,
brominated flame retardants, ammonium phosphate, ammonium
hydroxide, alumina trihydrate, and phosphate ester.
[0168] Materials to facilitate nucleation of the polymer may be
added. Such materials include nucleating agents. Nucleating agents
include, but are not limited to, sodium benzoate, dibenzylidene
sorbitol (DBS) and it chemical derivatives. Loading rates are
conventional.
[0169] Materials to color the layers may be added. Such colorant
materials are conventional.
[0170] In the manufacture of the instant battery separator, the
polymers may be co-extruded to form a multi-layered, nonporous
precursor, and then the precursor is processed to form the
micropores. Micropores may be formed by a `wet` process or a `dry`
process. The wet process (also referred as: solvent extraction,
phase inversion, thermally induced phase separation (TIPS), or gel
extraction) generally involves: the addition of a removable
material prior to the formation of the precursor, and subsequently
removing that material, for example, by an extraction process to
form the pores. The dry process (also referred to as the Celgard
process) generally involves: extruding a precursor (not including
any removal material for pore formation); annealing the precursor,
and stretching the precursor to form the micropores. The instant
invention will be discussed hereinafter with regard to the dry
process.
[0171] One way to describe the possibly preferred penta-layer
structure is an inverted tri-layer (PE/PP/PE) laminated between two
polypropylene layers:
Exemplary Additional Data Thereon
[0172] In accordance with at least selected embodiments, aspects,
or objects, the application, disclosure, or invention relates to
improved membranes, separator membranes, separators, battery
separators, secondary lithium battery separators, multilayer
membranes, multilayer separator membranes, multilayer separators,
multilayer battery separators, multilayer secondary lithium battery
separators, multilayer battery separators, batteries, capacitors,
super capacitors, double layer super capacitors, fuel cells,
lithium batteries, lithium ion batteries, secondary lithium
batteries, and/or secondary lithium ion batteries, and/or methods
for making and/or using such membranes, separator membranes,
separators, battery separators, secondary lithium battery
separators, batteries, capacitors, fuel cells, lithium batteries,
lithium ion batteries, secondary lithium batteries, and/or
secondary lithium ion batteries, and/or devices, vehicles or
products including the same, and/or the like.
[0173] In accordance with at least selected embodiments, the
application, disclosure or invention relates to improved membranes,
separator membranes, separators, battery separators, secondary
lithium battery separators, multilayer membranes, multilayer
separator membranes, multilayer separators, multilayer battery
separators, multilayer secondary lithium battery separators,
multilayer battery separators, electrochemical cells, batteries,
capacitors, super capacitors, double layer super capacitors, fuel
cells, lithium batteries, lithium ion batteries, secondary lithium
batteries, and/or secondary lithium ion batteries, and/or methods
for making and/or using such membranes, separator membranes,
separators, battery separators, secondary lithium battery
separators, electrochemical cells, batteries, capacitors, fuel
cells, lithium batteries, lithium ion batteries, secondary lithium
batteries, and/or secondary lithium ion batteries, and/or devices,
vehicles or products including the same, and/or the like.
[0174] Various embodiments of the invention have been described in
fulfillment of the various objects of the invention. It should be
recognized that these embodiments are merely illustrative of the
principles of the invention. Numerous modifications and adaptations
will be readily apparent to those skilled in the art without
departing from the spirit and scope of this invention.
[0175] As used in the specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the context clearly dictates otherwise. Ranges can be expressed
herein as from "about" or "approximately" one particular value,
and/or to "about" or "approximately" another particular value. When
such a range is expressed, another embodiment includes from the one
particular value and/or to the other particular value. Similarly,
when values are expressed as approximations, by use of the
antecedent "about," it will be understood that the particular value
forms another embodiment. It will be further understood that the
endpoints of each of the ranges are significant both in relation to
the other endpoint, and independently of the other endpoint.
"Optional" or "optionally" means that the subsequently described
event or circumstance can or cannot occur, and that the description
includes instances where said event or circumstance occurs and
instances where it does not.
[0176] Throughout the description and claims of this specification,
the word "comprise" and variations of the word, such as
"comprising" and "comprises," means "including but not limited to,"
and is not intended to exclude, for example, other additives,
components, integers, or steps. The terms "consisting essentially
of" and "consisting of" can be used in place of "comprising" and
"including" to provide for more specific embodiments of the
invention and are also disclosed. "Exemplary" or "for example"
means "an example of" and is not intended to convey an indication
of a preferred or ideal embodiment. Similarly, "such as" is not
used in a restrictive sense, but for explanatory or exemplary
purposes.
[0177] Other than where noted, all numbers expressing geometries,
dimensions, and so forth used in the specification and claims are
to be understood at the very least, and not as an attempt to limit
the application of the doctrine of equivalents to the scope of the
claims, to be construed in light of the number of significant
digits and ordinary rounding approaches.
[0178] Unless defined otherwise, all technical and scientific terms
used herein have the same meanings as commonly understood by one of
skill in the art to which the disclosed invention belongs.
Publications cited herein and the materials for which they are
cited are specifically incorporated by reference.
* * * * *